# Using programmable infusion pump in avian species – a validation methodology in geese

Myriam Trottier-paquet, Maude Gauthier-Bouchard, Akiko Kato, Charline

Parenteau, Frédéric Angelier, Pierre Legagneux

► To cite this version:

Myriam Trottier-paquet, Maude Gauthier-Bouchard, Akiko Kato, Charline Parenteau, Frédéric Angelier, et al.. Using programmable infusion pump in avian species – a validation methodology in geese. Wildlife Biology, In press, 10.1002/wlb3.01527. hal-05280095

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# WILDLIFE BIOLOGY

## Short Communication

### Using programmable infusion pump in avian species – a validation methodology in geese

Myriam Trottier-Paquet<sup>1</sup>, Maude Gauthier-Bouchard<sup>2</sup>, Akiko Kato<sup>3</sup>, Charline Parenteau<sup>3</sup>, Frédéric Angelier<sup>3</sup> and Pierre Legagneux<sup>1,3</sup>

**Correspondence:** Myriam Trottier-Paquet (myriam.trottier-paquet.1@ulaval.ca)

### Wildlife Biology

2025: e01527

doi: 10.1002/wlb3.01527

Subject Editor: Mathieu Leblond

Editor-in-Chief: Ilse Storch

Accepted 14 August 2025

<figure><img src="image_3.png" /></figure>

Wildlife face anthropogenic and natural stressors that affect their physiology and behaviour. The activity of the hypothalamic-pituitary-adrenal axis and glucocorticoid (GC) production is intrinsically linked with energy regulation and environmental stressors. Understanding the physiological mechanisms behind animals' decisions requires experiments that manipulate GC levels and measure behavioural or life-history outcomes. Current phenotypic engineering experiments lack the ability to deliver hormones in a pulsatile or circadian manner, limiting our ability to mimic chronic stress or isolate the effects of capture and handling from GC manipulation. We developed a method to externally attach commercial programmable infusion pumps (iPrecio SMP-200) to birds to deliver hormones subcutaneously at pre-programmed rates. We tested this method on five semi-captive Canada geese *Branta canadensis* and five greater snow geese *Anser caerulescens atlanticus*, monitoring changes in body mass, wound healing, and the operational state of the pumps. In snow geese, we conducted a hormonal experiment by delivering adrenocorticotropic hormone (ACTH) via the pumps to stimulate GC production. We then measured body mass at three time points, recorded activity using dynamic body acceleration, and collected fecal samples daily to assess corticosterone levels (the main GC in birds). Pumps were deployed for 11 to 14 days, with 7 out of 10 remaining functional throughout. One bird showed minor inflammation, but no apparent adverse effects on body mass or activity were observed. ACTH delivery led to significant increases in fecal corticosterone levels and dynamic body acceleration. This study represents the first successful external use of iPrecio pumps in birds and provides a promising tool for investigating circadian hormone dynamics, chronic stress, and ecotoxicology in wild species under more natural conditions.

Keywords: Glucocorticoids, programmable infusion pumps, stress physiology experiment, Canada geese, greater snow geese, adrenocorticotropic hormone (ACTH)

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<footnote n="1"><sup>1</sup>Université Laval, Département de Biologie & Centre d'Études Nordiques, Québec, Canada</footnote>

<footnote n="2"><sup>2</sup>Clinique vétérinaire de St-Césaire, Saint-Césaire, Canada</footnote>

<footnote n="3"><sup>3</sup>Centre d'Etudes Biologiques de Chizé, CNRS-La Rochelle Université, UMR, Villiers en Bois, France</footnote>
## Introduction

Wild animals can cope with environmental stressors via processes operating at different biological scales (from cellular to physiological and behavioural responses) and across different time scales, ranging from immediate reactions to delayed responses such as migration and reproduction (Wingfield 2008). Human activities introduce additional and often novel stressors to organisms across all biomes, resulting in both lethal and sublethal effects on wildlife populations (Katzner et al. 2020). Such activities can induce physiological and behavioral changes that directly impact life-history traits. To cope with anthropogenic disturbance, animals must assess risks and respond adaptively to maximize their fitness (Wingfield 2003, Smith et al. 2021, 2024). Multiple stressors may interact in complex ways – additively, synergistically, or antagonistically – further complicating efforts to disentangle their effects (Côté et al. 2016, Grunst et al. 2023). Measuring organism's response to multiple stressors in the wild is logistically challenging, yet crucial for developing a mechanistic understanding of their impact that is essential for implementing effective conservation measures (Pirotta et al. 2018).

Both anthropogenic and natural stressors are typically unpredictable and can elicit similar physiological responses, such as the activation of a stress response analogous to that triggered by predator presence (Frid and Dill 2002). In vertebrates, such stressors activate the hypothalamic–pituitary–adrenal (HPA) axis, leading to the production of glucocorticoids (GCs) (Wingfield et al. 1998, Angelier and Wingfield 2013, Blas and Fairhurst 2022). GCs are a class of steroid hormones produced by the adrenal cortex, with corticosterone (CORT) being the main GC circulating in most bird species. At low, baseline levels, GCs fluctuate to help regulate food intake and energy mobilization in preparation for daily needs or high-energy demands associated with specific life cycle events (Landys et al. 2006, Lennox et al. 2016). At elevated levels, GCs facilitate physiological and behavioral changes that help organisms cope with perturbations, such as danger or extreme events, and enhance immediate survival (Busch and Hayward 2009, Angelier and Wingfield 2013). When GCs are maintained at high levels for prolonged periods, however, they can have detrimental effects on animal health and fitness (Sapolsky et al. 2000, Busch and Hayward 2009). For example, in response to outdoor recreational activities, alpine black grouse *Tetrao tetrix* exhibit elevated concentrations of fecal CORT metabolites (Arlettaz et al. 2007) and show increased energy expenditure (Arlettaz et al. 2015).

Endocrine manipulation experiments can be used to gain a mechanistic understanding of the role of various hormones in physiology, behavior, and ultimately, the fitness of wild animals (Ketterson et al. 1996, Fusani 2008). Different techniques can be used to manipulate hormones in the field such as silastic implants (Angelier et al. 2007, Schultner et al. 2014), time release pellets (Almasi et al. 2008, Torres-Medina et al. 2018, Hoarau et al. 2022, 2025) and osmotic mini-pumps (Soma et al. 2000, Horton et al. 2007). However, most of these methods of endocrine manipulations

do not allow ecophysiologists to mimic the normal circadian or pulsatile release of hormones in wild animals (Ovid et al. 2018). For instance, implants and pellets typically deliver a high dose of hormone that potentially activates negative feedback mechanisms (Fusani 2008), leading to complex and non-linear modifications of circulating hormonal levels. Indeed, prolonged exposure to exogenous hormones via implants can suppress the endogenous production (Fusani 2008, Dantzer et al. 2016), and obscure natural variations occurring in the organism (Romero and Wingfield 2015, Dantzer et al. 2016, Fusani 2019).

Furthermore, animal capture in field experiments can induce major physiological and behavioral shifts through stress responses, and these shifts can potentially confound the measurements of variables of interest, particularly those related to stress physiology (Cattet et al. 2008, Morellet et al. 2009). A common practice to minimize these problems is to discard data collected 1 to 7 days after capture, depending on the species (Rosenblatt et al. 2021, Hoarau et al. 2025). Programmable infusion pumps, which can be implanted in small laboratory animals to deliver substances in a delayed and pulsatile manner (Abe et al. 2009), are a promising tool to overcome the above-mentioned limitations. For instance, programmable infusion pumps have been successfully used to deliver drugs at constant or variable infusion rates in mammals, from rats to primates (Tan et al. 2011), and have shown potential for further investigating the role of circadian hormones (Dantzer et al. 2016, Ovid et al. 2018, Fusani 2019). Here, we present a novel approach for externally attaching programmable infusion pumps to birds to deliver a solution via a subcutaneous catheter. We initially installed the pumps on five Canada geese *Branta canadensis* to develop and test the attachment procedure. We then fitted five greater snow geese *Anser caerulescens atlanticus* with the same pumps – with some adjustments in the procedure (Supporting information) – to deliver increasing volumes of adrenocorticotropic hormone (ACTH), a pituitary hormone that stimulates the adrenal cortex to release glucocorticoids.

Our primary goal was to validate both the reliability of the attachment system and the effectiveness of hormone delivery using this setup. As part of the validation process, we measured corticosterone concentrations in fecal samples (fCORT). In addition to fCORT levels, we monitored changes in body mass and activity levels derived from dynamic body acceleration using triaxial accelerometers mounted on neck collars. We compared these three metrics during and after ACTH administration to assess the effectiveness of the pumps in delivering ACTH to the geese. We conclude by discussing the potential applications of this method for future field studies in wildlife biology and ecotoxicology.

## Material and methods

### Study model and overview of the experimental design

In the spring of 2022, five Canada geese and five greater snow geese in semi-captivity were fitted with iPrecio pumps
(SMP-200; 2 × 4 × 1 cm; 7.9 g) at the Zoo Sauvage de Saint-Félicien (Québec, Canada). The geese were housed in an aviary composed of a 4 × 4m indoor compartment and a 4 × 12m outdoor compartment. Birds had ad libitum access to food and water throughout the study. Geese had been brought into the aviary in mid-October 2021 to over-winter. On 28 March, Canada and greater snow geese were separated in different outdoor enclosures (each measuring 24 m²), where they remained until the end of the experiment on 27 April. On 28 March, we measured body mass, tar-sus length and head length. We first deployed the pumps on Canada geese on 2 April for a 14-day period to develop and refine the attachment protocol. We assessed body mass, the operational and physical condition of the pumps, and wound healing upon pump removal on 16 April. In greater snow geese, we installed the pumps on 16 April and removed them on 27 April.

We programmed the pumps to begin infusion after a 24-h rest period following deployment. ACTH was administered over a 5-day infusion period by the pumps using an increasing daily dose. The pumps then remained in place without delivering solution for an additional 5-day post-infusion period. We measured body mass on day 0 (pump deployment), at the end of the infusion period, and at the end of the post-infusion period. We mounted Axy 5S accelerometers (TechnoSmArt, Italy) on standard 15 g collars typically used to monitor wild greater snow geese (LeTourneux et al. 2024), which recorded tri-axial acceleration between -8 and +8 G at a frequency of 25 Hz throughout the pump deployment period. To minimize behavioral biases, we fitted birds with dummy collars identical in size and weight prior to the start of data collection to allow habituation. Fresh feces were collected daily around 8 a.m., stored individually in Whirlpack bags labeled with species, date and time of collection, and frozen at -20°C on site within 30 min. A summary of the experimental design and data collection for greater snow geese is provided in Table 1 (see the Supporting information for Canada geese).

## Pump preparation and installation

We programmed the pumps and filled them with 900 µl of a solution of Human ACTH I-24 (AnaSpec AS-2061; 0.001 mg µl⁻¹) the day before surgery, then stored them at 4°C. To protect the reservoir, we fitted a 4 cm piece of heat shrink tubing using a heat gun. This covered the pump from the side handles to the top, where it was sealed with pliers. No direct heat was applied over the reservoir. The catheter was never touched and was protected from the heat by a metal plate. We activated the pumps immediately prior to surgery. We cushioned the surgical table with a clean towel and placed a second rolled towel under the chest and neck of the goose. We positioned the goose on its belly with its neck elongated, and placed a clean sock over its head to help reduce stress.

The surgical procedure was performed by a veterinarian following the detailed protocol available in the Supporting information. A 2.5 × 4 cm surgical area at the base of the

<table><caption>Table 1. Experimental design, ACTH dosage and calendar of experiments, sampling and data collection conducted on 5 greater snow geese at the Zoo Sauvage de St-Félicien in April 2022.</caption><thead><tr><th>Day in April</th><th>16</th><th>17</th><th>18</th><th>19</th><th>20</th><th>21</th><th>22</th><th>23</th><th>24</th><th>25</th><th>26</th><th>27</th></tr><tr><th>Period of the day</th><th>AM</th><th>PM</th><th>AM</th><th>PM</th><th>AM</th><th>PM</th><th>AM</th><th>PM</th><th>AM</th><th>PM</th><th>AM</th><th>PM</th></tr><tr><th>Experimental day</th><th></th><th>D0</th><th>D1</th><th>D2</th><th>D3</th><th>D4</th><th>D5</th><th>D6</th><th>D7</th><th>D8</th><th>D9</th><th>D10</th></tr><tr><th>Treatment</th><th></th><th>rest</th><th></th><th></th><th colspan="5">infusion</th><th colspan="5">post-infusion</th></tr></thead><tbody><tr><td>ACTH dose administered (µG/KG/DAY)</td><td></td><td>0</td><td>10</td><td>20</td><td>40</td><td>60</td><td>80</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td></tr><tr><td>Infusion rate (µG/KG/hr)</td><td></td><td>0</td><td>0.42</td><td>0.83</td><td>1.67</td><td>2.5</td><td>3.33</td><td>0</td><td>0</td><td>0</td><td>0</td><td>0</td></tr><tr><td>Pumps</td><td colspan="12">deployed</td></tr><tr><td>Accelerometers</td><td colspan="12">deployed</td></tr><tr><td>Body mass</td><td></td><td>X</td><td></td><td></td><td></td><td></td><td></td><td>X</td><td></td><td></td><td></td><td>X</td></tr><tr><td>N feces analyzed</td><td>5</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>4</td><td>0</td></tr></tbody></table>
neck was plucked, locally anesthetized and disinfected. The catheter, with a slit in the middle to allow the substance to be delivered, was inserted subcutaneously through an initial incision and exited through a second incision where it was ligated and secured to the skin (Fig. 1). Both incisions were closed with a single horizontal mattress stitch, and a thin layer of silver sulfadiazine cream was applied to the wounds to prevent infection.

We secured the pump following standard protocol for attaching tracking devices to seabirds and waterbirds (Wilson et al. 1997, Elliott et al. 2014). Posterior to the surgical area, we wrapped four overlapping strips of waterproof adhesive tape (TESA) around the feathers and the pump. To conceal and limit access to the wounds and the pump, we applied a thin layer of latex-based skin adhesive (Osto-Bond) to the top of the taped pump and folded the lateral and anterior feathers back over the surgical area and onto the pump. We then applied a piece of Tegaderm transparent film dressing in place to cover both the surgical area and the pump. Using absorbable sutures and fixation to the back feathers eliminates the need for a second invasive surgery to remove the pump, unlike subcutaneous osmotic pumps, which must be implanted internally (Fusani 2019, Blas and Fairhurst 2022). Detailed step-by-step surgical procedures, including wound care and pump attachment, are provided in the Supporting information.

## ACTH administration and CORT analyses

We tested the ability of the infusion pump to deliver hormones by administering adrenocorticotropic hormone (ACTH), a pituitary hormone that stimulates CORT release. ACTH is known to elevate CORT levels measured in droppings (Legagneux et al. 2011). The administration of ACTH through the pump should result in an increase in CORT levels in droppings directly originating from circulating plasma CORT (Legagneux et al. 2011). To prevent saturation and to stimulate CORT production throughout the course of

the experiment, the delivery rate of ACTH was increased daily. Higher ACTH concentrations serve to prolong rather than increase glucocorticoid release (Dallman et al. 1987). During the 5-day infusion period (day 1 to day 5), ACTH was delivered at a constant rate that was increased every 24 h (0.01, 0.02, 0.04, 0.06, 0.08 mg kg⁻¹ day⁻¹; Table 1). During the post-infusion period (day 6 to day 10), no ACTH was delivered. The infusion protocol used for the greater snow geese followed the same approach used in greylag geese *Anser anser*, where increasing ACTH doses maintained elevated plasma CORT levels over a period of five days (Legagneux and Hoarau unpubl.).

At the end of the experiment, we transferred the collected fecal samples from -20°C to -80°C until laboratory analyses were conducted. We oven-dried the dropping samples at 60°C for 48 h and homogenized them with a RETSCH MM400 mixer mill at 30 Hz for 30 s. We selected and prepared for analysis a subset of at least four fecal samples per species per day available, by weighing 100 mg (±0.8 SE) of ground droppings into a glass tube for extraction. At the Centre d'Etudes Biologiques de Chizé, each sample was mixed with 1 ml of 80% methanol. The mixture was homogenized for 30 min at 2500 RPM, then centrifuged for 15 min at 4000 RPM. We collected 600 µl of the supernatant, which was evaporated under nitrogen at 60°C. The dried extract was re-dissolved in phosphate buffer and incubated overnight at 4°C with 3000 CPM of ³H-corticosterone (reference NEZ033H005MC, Perkin Elmer, US) and a polyclonal rabbit antiserum (reference C8784 Sigma, US). The bound and free fractions were separated by adding dextran-coated charcoal. After centrifugation, activity of the bound fraction was measured in a Tri-carb liquid scintillation counter 2810TR (Perkin Elmer, US). Each sample was measured in duplicate. Intra and inter-assay variation was 10.30% and 10.62% respectively. The lowest detectable concentration was 0.23 pg/mg while the lowest measurement was 34.02 pg mg⁻¹.

<figure><img src="image_5.png" /><figcaption>Figure 1. Schematic representation of the I pump SMP-200 installed externally at the base of the neck of a snow goose containing a solution of ACTH (in blue). Solution was delivered through a small slit of 0.4 cm long in the subcutaneous section of the catheter at a predetermined pace. A heat-shrink tube (not shown) was placed above the blue reservoir for protection. The pump was secured externally to the back feathers using TESA tape and glue (not shown). Once released, the pump was not visible as it was covered by feathers. See the Supporting information for a detailed surgical procedure.</figcaption></figure>
## Statistical analysis

We conducted data exploration using the protocol described in Zuur et al. (2010). We performed all statistical analyses using R ver. 4.2.2 (www.r-project.org).

To test for the impact of the pump deployment on body condition, we used paired t-tests to compare body mass before and after the deployment of the pump for each species, using the ‘rstatix’ package ver. 0.7.2 (Kassambara 2023). In snow geese, we conducted an additional paired t-test to compare body mass before and after ACTH administration, in order to assess the effect of the hormonal treatment. p-values were adjusted to account for multiple comparisons using the Holm-Bonferroni correction.

In greater snow geese, we investigated the effects of ACTH administration by comparing our variables of interest - fecal corticosterone and accelerometry-based activity levels - between the infusion and post-infusion periods. Data collected during the 24 h following surgery (day 0) were excluded from the analysis to avoid potential confounding effects of handling and surgery.

Fecal samples collected before the pump installation (pre-pump) provide an approximation of the fCORT baseline level. To test for differences in fCORT between the pre-pump (n=5 samples), the infusion (n=20 samples), and the post-infusion (n=16 samples) period, we used a linear mixed model, with the date of feces collection as a random intercept to account for temporally grouped data. This analysis was conducted using the ‘lme4’ package ver. 1.1.35.5 (Bates et al. 2015).

Triaxial accelerometers record the total acceleration which is the result of the static component (the gravitational force) and the dynamic component of the acceleration over 3 axes. Dynamic body acceleration is known to reflect energy expenditure across a range of species (Halsey et al. 2009, Gleiss et al. 2011, Qasem et al. 2012, Wilson et al. 2020). In geese, accelerometers placed on the neck allow for behavioral discrimination (Lameris et al. 2021, Hoarau et al. 2025). We first approximated static acceleration using a smoothing function over 1 second (Wilson et al. 2006) in IGOR Pro (ver. 9.0.5.1 Wavemetrics, USA). For each axis, we then calculated dynamic acceleration by subtracting the static component from the total acceleration. Finally, we computed the vectorial dynamic body acceleration (VDBA) using the following equation.

$$VDBA = \sqrt{Adx^2 + Ady^2 + Adz^2}$$

We used the hourly means of the VDBA as a proxy for activity level and log-transformed the data to ensure normality. To test if the ACTH treatment affected activity levels, we fitted a linear mixed model using the ‘lme4’ package ver. 1.1.35.5 (Bates et al. 2015), with individual ID as a random intercept. We compared the hourly means of VDBA between infusion and post-infusion periods. Since higher activity levels are expected during daylight hours (from 30 min before sunrise to 30 min after sunset), we included the period of the day (night versus day) as a covariate in the model.

## Results

In 2022, surgery was performed on five Canada geese on 2 April and on five snow geese on 16 April. The weight of the filled pump was 8.8 g representing 0.2–0.3% of the bird’s body weight (mean body weight in Canada geese = 4192 g; range [3882–4685] and mean body weight in snow geese = 3044 g; range [2403–3838]). The average surgery duration (from local anesthesia to release into the enclosure) was 33.2 min, including the 5-min waiting period after drug administration. After 14 days on the backs of the Canada geese, three of the five pumps remained in place. However, a technical malfunction in the communication device prevented proper activation of the first four pumps, meaning only one individual received ACTH as intended. Full details of this partial treatment are provided in the Supporting information.

The protocol was subsequently refined before deployment in snow geese (Supporting information). In this second group, all five pumps were successfully activated and remained in place after 11 days. However, one male chewed through the protective shrink sleeve, puncturing the pump reservoir. It was not possible to determine when this individual stopped receiving the ACTH. Details on the outcome and causes of failure for each individual are available in the Supporting information.

Although statistical tests could not be conducted due to the small sample size, pump setup disruptions appeared more frequent in males. In Canada geese, two of four males disrupted the setup, while the single female did not. In snow geese, one of the two males caused a disruption, and no disruptions were observed in females (Supporting information). During the post-experiment follow-up, the veterinarian observed a localized inflammatory reaction around the catheter in a single male Canada goose, while the other nine individuals showed normal and rapid healing. In the months that followed, no adverse effects of the procedure were observed in either Canada or snow geese.

### Effect of the pump and the ACTH treatment on body mass

We found no significant change in body mass between the day of pump installation and the day of retrieval for either Canada geese (t(4) = 0.430, p = 0.689, 95% CI: [-143, 195]) or snow geese (t(4) = 0.995, p = 0.752, 95% CI: [-81, 171]). In greater snow geese, there was no significant difference between the body mass before and after the infusion period (t(4) = 0.724, p = 0.752, 95% CI: [-64, 108]).

### Feces corticosterone content

In greater snow geese, where at least four individuals received the full ACTH treatment, mean fecal corticosterone concentrations during ACTH administration were 215.4 pg mg⁻¹, compared to 140.0 pg mg⁻¹ during the post-infusion period (difference = 75.4 pg mg⁻¹ (95% CI: [10, 141]). In contrast, mean fCORT levels during the pre-pump period were 148.9, similar to the post-infusion period (difference = 8.9 pg mg⁻¹; 95% CI: [-95, 113]). Full model results are presented in Table 2 and corresponding distributions are shown in Fig. 2.
<table><caption>Table 2. Parameter estimates and 95% confidence intervals (CI) from the linear mixed model of fecal corticosterone content in droppings (pg mg⁻¹ of dry material) collected daily in the enclosure of five greater snow geese before the pump installation (pre-pump, n=5 samples), during the 5-day infusion period while receiving an increasing dose of ACTH (n=20 samples) and during the 5-day post-infusion period (n=16 samples). Date of feces collection was included as a random intercept. Estimates represent the mean fCORT concentrations for each period. The post-infusion period is the reference level. Confidence intervals that do not overlap zero indicate statistically significant differences from the reference period and are in bold.</caption><thead><tr><th></th><th>Estimate</th><th>95% CI</th><th>t-value</th></tr></thead><tbody><tr><td>Intercept</td><td><strong>140.02</strong></td><td><strong>91.33, 188.71</strong></td><td><strong>5.16</strong></td></tr><tr><td>Period [pre-pump]</td><td>8.89</td><td>-95.29, 113.08</td><td>0.15</td></tr><tr><td>Period [infusion]</td><td><strong>75.4</strong></td><td><strong>10.07, 140.72</strong></td><td><strong>2.07</strong></td></tr></tbody></table>

## Body acceleration

For the snow geese, the average VDBA was about 1.23 (95% CI: [1.15, 1.31]) fold higher during the ACTH treatment than during the control period (Fig. 3, Table 3). The effect of the treatment was even stronger (1.28, 95% CI: [1.19, 1.37]) when we removed from the analysis the data from the individual with the punctured reservoir, which indicates that it might not have received the complete treatment.

## Discussion

This study provides the first successful demonstration of externally attached programmable infusion pumps (iPrecio) in birds. This technique involves a subcutaneous catheter connected to a pump fixed to the back feathers with TESA tape and glue. Our results indicate that the method is minimally invasive, well tolerated by the birds, and does not seem to impair body condition. Corticosterone levels measured during the post-infusion period were comparable to baseline

values – although based on only five samples – suggesting no major impact of the pump on GC levels. The surgical procedure takes less than 30 min, offering a practical and ethical alternative to subcutaneous implants for field use (Fusani 2019, Blas and Fairhurst 2022). We expect that, under natural conditions, the device could remain in place for less than two months or until molting, although retention duration should be properly documented in future studies. A comparable attachment method (e.g. 8.4 g device with TESA tape and sutures) in long-tailed ducks *Clangula hyemalis* showed retention for 26 days (range: 16–34 days; Enstipp et al. 2015). The pump was fixed on the upper back of the bird, in a position previously used for other devices in goose research that have not been associated with impaired flight (Lameris et al. 2018, Hoarau et al. 2025). While externally attached devices can affect the physiology and behaviour of birds (Barron et al. 2010, Enstipp et al. 2015, Lameris et al. 2018, Geen et al. 2019), those using glue or tape tend to cause less abrasion and disruption than harnesses (Barron et al. 2010, Lameris and Kleyheeg 2017). They also typically have minimal impact on nesting success or device-induced behaviours (Barron et al. 2010). We believe that the temporary nature of the attachment, combined with the relatively small weight and size of the pump and its concealment within feathers, helps minimize aerodynamic drag and mitigates potential physiological and behavioural impacts.

Although our study relied on small sample sizes, the ACTH infusion in greater snow geese successfully triggered a 54% increase in fecal CORT levels and elevated dynamic body acceleration, supporting the physiological effectiveness of the hormone delivery via the pump. While no impact on body mass was observed after the infusion period, prolonged elevation of CORT level might have prevented weight gain, as shown in passerine birds (Bauer et al. 2022). Technical challenges were addressed through protocol refinements. Improvements successfully prevented catheter pull-out in the

<figure><img src="image_6.png" /><figcaption>Figure 2. Corticosterone content in droppings (fCORT) collected daily from the enclosure of five greater snow geese before pump installation (n=5 samples), during the infusion period with increasing doses of ACTH (n=20 samples), and during the post-infusion period (n=16 samples). Different letters indicate statistically significant differences between periods based on a linear mixed-effect model (95% CI does not overlap zero). Boxplots show the median, 25th and 75th percentiles; shaded points represent raw data.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Figure 3. Mean hourly acceleration data (vectorial dynamic body acceleration) of greater snow goose (n = 5 individuals) during the 5-day infusion period with increasing doses of ACTH compared to the 5-day post-infusion period. Asterisks indicate statistically significant differences between periods within each light condition based on the linear mixed model (95% CI does not overlap zero). Boxes represent the back-transformed model predicted means with 95% confidence intervals; shaded points show the raw data.</figcaption></figure>

second experiment on snow geese. One reservoir was damaged by a snow goose, but this issue can certainly be avoided in future studies by reorienting the pump downward. All surgical and attachment protocols are detailed in the Supporting information to support reproducibility.

## Perspectives

The ability to program substance delivery – either continuously, rhythmically, or with a delayed onset – opens exciting possibilities for field-based studies in ecology and physiology. Combined with GPS and accelerometry (Yu et al. 2023, Hoarau et al. 2025), iPrecio pumps could allow researchers to assess the real-time behavioral and physiological effects of hormonal or chemical manipulations in free-living animals.

In stress physiology, the experimental manipulation of GCs has been widely used, but prolonged treatment typically leads to reduced endogenous production. Additionally, the stress of capture and handling is difficult to distinguish from the experimental treatment (Fusani 2019, Blas and Fairhurst

2022). Currently, no known methodology can induce corticosterone levels associated with chronic stress in the field (Romero and Wingfield 2015). Chronic stress causes frequent pulsatile increases in corticosterone production, leading to a sustained moderate elevation in plasma CORT, a condition which is impossible to reproduce in the wild using classic implants (Strochlic and Romero 2008). The programmable feature of the iPrecio pump offers an alternative as it allows for the delayed and pulsatile release of substances, enabling the separation of capture-related stress from hormone administration effects while reducing the magnitude of endogenous feedback regulation. Furthermore, it also allows for maintaining the natural diel rhythm (Breuner et al. 1999, Romero and Remage-Healey 2000, Rich and Romero 2001, Scheiber et al. 2017) in hormone diffusion, whatever the concentration used, and this cannot be replicated using pellets or implants.

There remains a significant gap in our understanding of the role of hormones throughout all phases of bird migration

<table><caption>Table 3. Parameter estimates and 95% confidence intervals (CI) from the linear mixed model of vectorial dynamic body acceleration (VDBA - log-transformed hourly average VDBA + 0.01 was used to normalize the data) from greater snow geese (n = 5 individuals) during the 5-day infusion period while receiving an increasing dose of ACTH and during the 5-day post-infusion period. Day/night was included as a fixed effect and the individual ID was included as a random intercept. The intercept represents the post-infusion period during the daytime. Back-transformed estimates reflect fold changes in average VDBA relative to the reference category (post-infusion, daytime). Confidence intervals that do not include zero (or Back-transformed CI that do not include one) indicate significant differences and are in bold.</caption><thead><tr><th rowspan="2"></th><th colspan="3">Log-transformed hourly average VDBA</th><th colspan="2">Back-transformed hourly average VDBA</th></tr><tr><th>Estimate</th><th>95% CI</th><th>t value</th><th>Estimate</th><th>95% CI</th></tr></thead><tbody><tr><td>Intercept</td><td>-1.73</td><td>-1.92, -1.53</td><td>-18.85</td><td>0.18</td><td>0.14, 0.21</td></tr><tr><td>Period [Infusion]</td><td>0.22</td><td>0.15, 0.28</td><td>6.73</td><td>1.23</td><td>1.15, 1.31</td></tr><tr><td>Day/night [night]</td><td>-0.87</td><td>-0.93, -0.81</td><td>27.48</td><td>0.41</td><td>0.39, 0.44</td></tr></tbody></table>
(Cornelius et al. 2013). For instance, whether corticosterone contributes to migration preparation, signals the departure or helps sustain the migratory flight remains a topic of ongoing debate (DeSimone et al. 2020, Bauer and Watts 2021). For example, the chicken gut hormone ghrelin was recently found to modulate movement and stopover departure decisions in garden warblers *Sylvia borin* and yellow-rumped warblers *Setophaga coronata coronata* (Goymann et al. 2017, Lupi et al. 2022). The physiological mechanisms underlying different migratory strategies could be regulated by endocrine control, yet they remain poorly understood (Ramenofsky et al. 2012, Watts et al. 2018, Watts and Cornelius 2024). Although the sample size was limited in our study, the technical novelty of our approach offers a valuable tool to manipulate circadian and pulsatile hormone release, opening new possibilities for experimentally altering hormonal levels and advancing our understanding of migration strategies and the underlying mechanisms. In the field of phenotypic engineering – the experimental modification of individual traits via endocrine pathways to assess the fitness consequences (Ketterson et al. 1996) – there is ongoing debate about the appropriate control for endocrine manipulation, with some researchers proposing low-dose treatments as the most suitable option (Fusani 2008). The pumps offer precise programmability, enabling the controlled delivery of very low doses to designated individuals.

In ecotoxicology, the effects of contaminants and their degradation products are typically assessed through captive studies using model species such as partridge, quails, or ducks, exposed to increasing contaminant concentrations (Tassin de Montaigu and Goulson 2020). While these studies help establish dose-response relationships and inform regulation, they provide limited insight into the consequences of exposure in wild animals. Pesticides and herbicides can disrupt natural behaviours in wild birds even at low concentrations. For instance, ingestion of a single seed coated with neonicotinoids and chlorpyrifos has been shown to impair migratory behaviour, condition and orientation in white-crowned sparrows *Zonotrichia leucophorys* (Eng et al. 2017, 2019). We believe our proposed methodology offers a new avenue to experimentally assess the effects of emerging contaminants – including at low doses, alone or in combination – under natural conditions. When combined with lightweight biologists, this approach could reveal dose-dependent impacts on behaviour, life-history decisions and fitness in wild bird species.

*Acknowledgements* – We would like to thank Alexandra Coutu, Marcel Paquet and Matthieu Weiss-Blais for assistance in field operations and the direction of the Zoo Sauvage de Saint Félicien. Marie-Claude Martin provided guidance on the design of the study and ethical demands.

*Funding* – This work was supported by the Natural Sciences and Engineering Research Council of Canada, Sentinelle Nord program from the Canada First Research Excellence Fund and CNRS-France. *Permits* – All manipulations and procedures presented in this paper were approved by the “Comité de Protection des Animaux de

l'Université Laval" (CPAUL 2020-700, VRR-20-700) delivered the 2021-02-10.

## Author contributions

**Myriam Trottier-Paquet:** Conceptualization (supporting); Data curation (lead); Formal analysis (lead); Investigation (equal); Methodology (equal); Visualization (lead); Writing – original draft (lead). **Maude Gauthier-Bouchard:** Investigation (equal); Methodology (equal); Writing – review and editing (equal). **Akiko Kato:** Data curation (supporting); Writing – review and editing (equal). **Charline Parenteau:** Resources (equal); Writing – review and editing (equal). **Frédéric Angelier:** Resources (equal); Supervision (equal); Writing – review and editing (equal). **Pierre Legagneux:** Conceptualization (lead); Methodology (equal); Resources (equal); Supervision (equal); Writing – review and editing (equal).

## Transparent peer review

The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer-review/wlb3.01527.

## Data availability statement

Data and code are available from Zenodo: https://doi.org/10.5281/zenodo.16952764 (Trottier-Paquet et al. 2025).

## Supporting information

The Supporting information associated with this article is available with the online version.

## References

Abe, C., Tashiro, T., Tanaka, K., Ogihara, R. and Morita, H. 2009. A novel type of implantable and programmable infusion pump for small laboratory animals. – J. Pharmacol. Toxicol. Methods 59: 7–12.

Almasi, B., Roulin, A., Jenni-Eiermann, S. and Jenni, L. 2008. Parental investment and its sensitivity to corticosterone is linked to melanin-based coloration in barn owls. – Horm. Behav. 54: 217–223.

Angelier, F. and Wingfield, J. C. 2013. Importance of the glucocorticoid stress response in a changing world: theory, hypotheses and perspectives. – Gen. Comp. Endocrinol. 190: 118–128.

Angelier, F., Clément-Chastel, C., Gabrielsen, G. W. and Chastel, O. 2007. Corticosterone and time-activity budget: an experiment with black-legged Kittiwakes. – Horm. Behav. 52: 482–491.

Arlettaz, R., Patthey, P., Baltic, M., Leu, T., Schaub, M., Palme, R. and Jenni-Eiermann, S. 2007. Spreading free-riding snow sports represent a novel serious threat for wildlife. – Proc. R. Soc. B 274: 1219–1224.

Arlettaz, R., Nusslé, S., Baltic, M., Vogel, P., Palme, R., Jenni-Eiermann, S., Patthey, P. and Genoud, M. 2015. Disturbance of wildlife by outdoor winter recreation: allostatic stress response and altered activity-energy budgets. – Ecol. Appl. 25: 1197–1212.
Barron, D. G., Brawn, J. D. and Weatherhead, P. J. 2010. Meta-analysis of transmitter effects on avian behaviour and ecology. – Methods Ecol. Evol. 1: 180–187.

Bates, D., Mächler, M., Bolker, B. and Walker, S. 2015. Fitting linear mixed-effects models using lme4. – J. Stat. Softw. 67: 1–48.

Bauer, C. M. and Watts, H. E. 2021. Corticosterone's roles in avian migration: assessment of three hypotheses. – Horm. Behav. 135: 105033.

Bauer, C. M., Oranges, M. A., Firemonger, G. and Romero, L. M. 2022. Corticosterone alters body weight, but not metabolites, during chronic stress. – Physiol. Biochem. Zool. 95: 465–473.

Blas, J. and Fairhurst, G. D. 2022. Stress ecophysiology. – In: Sturkie's avian physiology. Elsevier, pp. 1049–1098.

Breuner, C. W., Wingfield, J. C. and Romero, L. M. 1999. Diel rhythms of basal and stress-induced corticosterone in a wild, seasonal vertebrate, Gambel's white-crowned sparrow. – J. Exp. Zool. 284: 334–342.

Busch, D. S. and Hayward, L. S. 2009. Stress in a conservation context: a discussion of glucocorticoid actions and how levels change with conservation-relevant variables. – Biol. Conserv. 142: 2844–2853.

Cattet, M., Boulanger, J., Stenhouse, G., Powell, R. A. and Reynolds-Hogland, M. J. 2008. An evaluation of long-term capture effects in ursids: implications for wildlife welfare and research. – J. Mammal. 89: 973–990.

Cornelius, J. M., Boswell, T., Jenni-Eiermann, S., Breuner, C. W. and Ramenofsky, M. 2013. Contributions of endocrinology to the migration life history of birds. – Gen. Comp. Endocrinol. 190: 47–60.

Côté, I. M., Darling, E. S. and Brown, C. J. 2016. Interactions among ecosystem stressors and their importance in conservation. – Proc. R. Soc. B 283: 20152592.

Dallman, M. F., Akana, S. F., Cascio, C. S., Darlington, D. N., Jacobson, L. and Levin, N. 1987. Regulation of ACTH secretion: variations on a theme of B. – In: Clark, J. H. (ed.), Proc. 1986 Laurentian Hormone Conf.. Recent Progress in Hormone Research. Academic Press, pp. 113–173.

Dantzer, B., Westrick, S. E. and van Kesteren, F. 2016. Relationships between endocrine traits and life histories in wild animals: insights, problems and potential pitfalls. – Integr. Comp. Biol. 56: 185–197.

DeSimone, J. G., Ramirez, M. G., Elowe, C. R., Griego, M. S., Breuner, C. W. and Gerson, A. R. 2020. Developing a Stopover-CORT hypothesis: corticosterone predicts body composition and refueling rate in gray catbirds during migratory stopover. – Horm. Behav. 124: 104776.

Elliott, K. H., Chivers, L. S., Bessey, L., Gaston, A. J., Hatch, S. A., Kato, A., Osborne, O., Ropert-Coudert, Y., Speakman, J. R. and Hare, J. F. 2014. Windscapes shape seabird instantaneous energy costs but adult behavior buffers impact on offspring. – Mov. Ecol. 2: 17.

Eng, M. L., Stutchbury, B. J. M. and Morrissey, C. A. 2017. Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird. – Sci. Rep. 7: 15176.

Eng, M. L., Stutchbury, B. J. M. and Morrissey, C. A. 2019. A neonicotinoid insecticide reduces fueling and delays migration in songbirds. – Science 365: 1177–1180.

Enstipp, M. R., Frost, J., Hollmén, T. E., Andrews, R. D. and Frost, C. 2015. Two methods of radio transmitter attachment and their effects on the behavior and energetics of captive long-

tailed ducks (*Clangula hyemalis*) during winter. – Anim. Biotelem. 3: 36.

Fusani, L. 2008. Endocrinology in field studies: problems and solutions for the experimental design. – Gen. Comp. Endocrinol. 157: 249–253.

Fusani, L. 2019. Field techniques in hormones and behavior. – Encycl. Anim. Behav.: 488–494.

Geen, G. R., Robinson, R. A. and Baillie, S. R. 2019. Effects of tracking devices on individual birds – a review of the evidence. – J. Avian Biol. 50: 1–13.

Gleiss, A. C., Wilson, R. P. and Shepard, E. L. C. 2011. Making overall dynamic body acceleration work: on the theory of acceleration as a proxy for energy expenditure. – Methods Ecol. Evol. 2: 23–33.

Goymann, W., Lupi, S., Kaiya, H., Cardinale, M. and Fusani, L. 2017. Ghrelin affects stopover decisions and food intake in a long-distance migrant. – Proc. Natl Acad. Sci. USA 114: 1946–1951.

Grunst, A. S., Grunst, M. L. and Fort, J. 2023. Contaminant-by-environment interactive effects on animal behavior in the context of global change: evidence from avian behavioral ecotoxicology. – Sci. Total Environ. 879: 163169.

Halsey, L. G., Shepard, E. L., Quintana, F., Laich, A. G., Green, J. A. and Wilson, R. P. 2009. The relationship between oxygen consumption and body acceleration in a range of species. – Comp. Biochem. Physiol. A 152: 197–202.

Hoarau, M., Angelier, F., Touzalin, F., Zgirski, T., Parenteau, C. and Legagneux, P. 2022. Corticosterone: foraging and fattening puppet master in pre-breeding greylag geese. – Physiol. Behav. 246: 113666.

Hoarau, M., Dulude-de Broin, F., LeTourneux, F., Angelier, F., Gauthier-Bouchard, M., Martin, M.-C., Kato, A., Lefebvre, J., Thomas, P. J., Williams, C. K., Bêty, J. and Legagneux, P. 2025. Bird migration on the edge: experimental manipulation of corticosterone advances departure dates. – Ecology 106: e70131.

Horton, B. M., Long, J. A. and Holberton, R. L. 2007. Intraperitoneal delivery of exogenous corticosterone via osmotic pump in a passerine bird. – Gen. Comp. Endocrinol. 152: 8–13.

Kassambara, A. 2023. rstatix: pipe-friendly framework for basic statistical tests. – R package ver. 0.7.0, https://cran.r-project.org/package=rstatix.

Katzner, T. E., Braham, M. A., Conkling, T. J., Diffendorfer, J. E., Duerr, A. E., Loss, S. R., Nelson, D. M., Vander Zanden, H. B. and Yee, J. L. 2020. Assessing population-level consequences of anthropogenic stressors for terrestrial wildlife. – Ecosphere 11: e03046.

Ketterson, E. D., Nolan Jr, V., Cawthorn, M. J., Parker, P. G. and Ziegenfus, C. 1996. Phenotypic engineering: using hormones to explore the mechanistic and functional bases of phenotypic variation in nature. – Ibis 138: 70–86.

Lameris, T. K. and Kleyheeg, E. 2017. Reduction in adverse effects of tracking devices on waterfowl requires better measuring and reporting. – Anim. Biotelem. 5: 24.

Lameris, T. K., Müskens, G. J. D. M., Kölzsch, A., Dokter, A. M., Van der Jeugd, H. P. and Nolet, B. A. 2018. Effects of harness-attached tracking devices on survival, migration, and reproduction in three species of migratory waterfowl. – Anim. Biotelem. 6: 7.

Lameris, T. K., Dokter, A. M., van der Jeugd, H. P., Bouten, W., Koster, J., Sand, S. H. H., Westerduin, C. and Nolet, B. A. 2021. Nocturnal foraging lifts time constraints in winter for
migratory geese but hardly speeds up fueling. – Behav. Ecol. 32: 539–552.

Landys, M. M., Ramenofsky, M. and Wingfield, J. C. 2006. Actions of glucocorticoids at a seasonal baseline as compared to stress-related levels in the regulation of periodic life processes. – *Gen. Comp. Endocrinol.* 148: 132–149.

Legagneux, P., Gauthier, G., Chastel, O., Picard, G. and Bêty, J. 2011. Do glucocorticoids in droppings reflect baseline level in birds captured in the wild? A case study in snow geese. – *Gen. Comp. Endocrinol.* 172: 440–445.

Lennox, R. J., Chapman, J. M., Souliere, C. M., Tudorache, C., Wikelski, M., Metcalfe, J. D. and Cooke, S. J. 2016. Conservation physiology of animal migration. – *Conserv. Physiol.* 4: cov072.

LeTourneux, F., Gauthier, G., Pradel, R., Lefebvre, J. and Legagneux, P. 2024. Evidence for seasonal compensation of hunting mortalities in a long-lived migratory bird. – *J. Appl. Ecol.* 61: 2169–2179.

Lupi, S., Morbey, Y. E., MacDougall-Shackleton, S. A., Kaiya, H., Fusani, L. and Guglielmo, C. G. 2022. Experimental ghrelin administration affects migratory behaviour in a songbird. – *Horm. Behav.* 141: 105139.

Morellet, N., Verheyden, H., Angibault, J.-M., Cargnelutti, B., Lourtet, B. and Hewison, M. A. J. 2009. The effect of capture on ranging behaviour and activity of the European roe deer *Capreolus capreolus*. – *Wildl. Biol.* 15: 278–287.

Ovid, D., Hayes, T. B. and Bentley, G. E. 2018. Melatonin administration methods for research in mammals and birds. – *J. Biol. Rhythms* 33: 567–588.

Piotta, E., Booth, C. G., Costa, D. P., Fleishman, E., Kraus, S. D., Lusseau, D., Moretti, D., New, L. F., Schick, R. S., Schwarz, L. K., Simmons, S. E., Thomas, L., Tyack, P. L., Weise, M. J., Wells, R. S. and Harwood, J. 2018. Understanding the population consequences of disturbance. – *Ecol. Evol.* 8: 9934–9946.

Qasem, L., Cardew, A., Wilson, A., Griffiths, I., Halsey, L. G., Shepard, E. L. C., Gleiss, A. C. and Wilson, R. 2012. Tri-axial dynamic acceleration as a proxy for animal energy expenditure; should we be summing values or calculating the vector? – *PLoS One* 7: e31187.

Ramenofsky, M., Cornelius, J. M. and Helm, B. 2012. Physiological and behavioral responses of migrants to environmental cues. – *J. Ornithol.* 153: 181–191.

Rich, E. L. and Romero, L. M. 2001. Daily and photoperiod variations of basal and stress-induced corticosterone concentrations in house sparrows (*Passer domesticus*). – *J. Comp. Physiol. B* 171: 543–547.

Romero, L. M. and Remage-Healey, L. 2000. Daily and seasonal variation in response to stress in captive starlings (*Sturnus vulgaris*): corticosterone. – *Gen. Comp. Endocrinol.* 119: 52–59.

Romero, L. M. and Wingfield, J. C. 2015. Tempests, poxes, predators and people: stress in wild animals and how they cope. – *Oxford Univ. Press*.

Rosenblatt, E., DeBow, J., Blouin, J., Donovan, T., Murdoch, J., Creel, S., Rogers, W., Gieder, K., Fortin, N. and Alexander, C. 2021. Juvenile moose stress and nutrition dynamics related to winter ticks, landscape characteristics, climate-mediated factors and survival. – *Conserv. Physiol.* 9: coab048.

Sapolsky, R. M., Romero, L. M. and Munck, A. U. 2000. How do glucocorticoids influence stress responses? Integrating permis- sive, suppressive, stimulatory and preparative actions. – *Endocr. Rev.* 21: 55–89.

Scheiber, I. B. R., de Jong, M. E., Komdeur, J., Pschernig, E., Loonen, M. J. J. E., Millesi, E. and Weiß, B. M. 2017. Diel pattern of corticosterone metabolites in Arctic barnacle goslings (*Branta leucopsis*) under continuous natural light. – *PLoS One* 12: e0182861.

Schultner, J., Moe, B., Chastel, O., Tartu, S., Bech, C. and Kitay- sky, A. S. 2014. Corticosterone mediates carry-over effects between breeding and migration in the Kittiwake *Rissa tridact- yla*. – *Mar. Ecol. Prog. Ser.* 496: 125–133.

Smith, J. A., Gaynor, K. M. and Suraci, J. P. 2021. Mismatch between risk and response may amplify lethal and non-lethal effects of humans on wild animal populations. – *Front. Ecol. Evol.* 9: 604973.

Smith, J. A., McDaniels, M. E., Peacor, S. D., Bolas, E. C., Cherry, M. J., Dorn, N. J., Feldman, O. K., Kimbro, D. L., Leonhardt, E. K., Peckham, N. E., Sheriff, M. J. and Gaynor, K. M. 2024. Population and community consequences of perceived risk from humans in wildlife. – *Ecol. Lett.* 27: e14456.

Soma, K. K., Tramontin, A. D. and Wingfield, J. C. 2000. Oestrogen regulates male aggression in the non-breeding season. – *Proc. R. Soc. B* 267: 1089–1096.

Strochlic, D. E. and Romero, L. M. 2008. The effects of chronic psychological and physical stress on feather replacement in European starlings (*Sturnus vulgaris*). – *Comp. Biochem. Physiol. A* 149: 68–79.

Tan, T., Watts, S. W. and Davis, R. P. 2011. Drug delivery: enabling technology for drug discovery and development. *iPRECIO*® micro infusion pump: programmable, refillable, and implantable. – *Front. Pharmacol.* 2: 44.

Tassin de Montaigu, C. and Goulson, D. 2020. Identifying agricultural pesticides that may pose a risk for birds. – *PeerJ* 8: e9526.

Torres-Medina, F., Cabezas, S., Marchant, T. A., Wikelski, M., Romero, L. M., Hau, M., Carrete, M., Tella, J. L. and Blas, J. 2018. Corticosterone implants produce stress-hyporesponsive birds. – *J. Exp. Biol.* 221: jeb173864.

Trottier-Paquet, M., Gauthier-Bouchard, M., Kato, A., Parenteau, C., Angelier, F. and Legagneux, P. 2025. Data and code from: Using programmable infusion pump in avian species – a validation methodology in geese. – *Zenodo*, https://doi.org/10.5281/zenodo.16952764.

Watts, H. E. and Cornelius, J. M. 2024. Toward understanding the endocrine regulation of diverse facultative migration strategies. – *Horm. Behav.* 158: 105465.

Watts, H. E., Cornelius, J. M., Fudickar, A. M., Pérez, J. and Ramenofsky, M. 2018. Understanding variation in migratory movements: a mechanistic approach. – *Gen. Comp. Endocrinol.* 256: 112–122.

Wilson, R. P., Pütz, K., Peters, G., Culik, B., Scolaro, J. A., Char-rassin, J.-B. and Ropert-Coudert, Y. 1997. Long-term attachment of transmitting and recording devices to penguins and other seabirds. – *Wildl. Soc. Bull.* 25: 101–106.

Wilson, R. P., White, C. R., Quintana, F., Halsey, L. G., Liebsch, N., Martin, G. R. and Butler, P. J. 2006. Moving towards acceleration for estimates of activity-specific metabolic rate in free-living animals: the case of the cormorant. – *J. Anim. Ecol.* 75: 1081–1090.

Wilson, R. P. et al. 2020. Estimates for energy expenditure in free-living animals using acceleration proxies: a reappraisal. – *J. Anim. Ecol.* 89: 161–172.

Wingfield, J. C. 2003. Control of behavioural strategies for capricious environment. – *Anim. Behav.* 66: 807–816.
Wingfield, J. C. 2008. Organization of vertebrate annual cycles: implications for control mechanisms. – Philos. Trans. R. Soc. B 363: 425–441.

Wingfield, J. C., Maney, D. L., Breuner, C. W., Jacobs, J. D., Lynn, S., Ramenofsky, M. and Richardson, R. D. 1998. Ecological bases of hormone-behavior interactions: the “emergency life history stage” 1. – Am. Zool. 38: 191–206.

Yu, H., Muijres, F. T. te Lindert, J. S., Hedenström, A. and Henningsson, P. 2023. Accelerometer sampling requirements for animal behaviour classification and estimation of energy expenditure. – Anim. Biotelem. 11: 28.

Zuur, A. F., Ieno, E. N. and Elphick, C. S. 2010. A protocol for data exploration to avoid common statistical problems. – Methods Ecol. Evol. 1: 3–14.