DOI: 10.5061/dryad.hx3ffbgmg
title: Data from: Comparative reproductive ecology of Old and New World Trogons, an order in decline across the world

description: Many tropical species show declining populations. The pantropical order
 Trogoniformes has 76% of its species ranked as declining, reflecting a
 world-wide problem. Here we report on the reproductive ecology and life
 history traits of the declining and near-threatened old world Whitehead’s
 Trogon (Harpactes whiteheadi), the declining new world Collared Trogon
 (Trogon collaris) and the stable Masked Trogon (T. personatus). We also
 reviewed the literature on reproductive ecology and life history traits of
 trogons to assess possible commonalities that might help explain
 population declines. We found that the declining Whitehead’s and Masked
 Trogons had reasonable nest success (32% and 25%, respectively), while the
 stable Masked Trogon had poor reproductive success (9%), all contrary to
 population trends. However, the limited literature data suggested that
 poor reproductive success may be common among trogons, which may
 contribute to population declines. Parents fed young at a low rate and had
 long on-bouts for incubation and nestling warming that reduced activity at
 the nest, as favored by high nest predation risk over evolutionary time.
 We found that young fledged from the nest with poorly developed wings, as
 also favored by high nest predation risk. Evolved nestling periods among
 trogon species suggests that poor wing development is likely common. Wing
 development has been shown to affect juvenile survival after leaving the
 nest. The poor wing development may be an important contributor to
 population declines that deserves more attention. Evolved life history
 traits are important to recognize as creating population vulnerabilities
 in a changing world.
description: Whitehead’s Trogon was studied in
 Kinabalu Park, Sabah, Malaysian Borneo (6° 05<em>'</em>N,
 116° 33<em>'</em>E), a 754 km<sup>2</sup>
 protected area of primary forest. Research was conducted during the
 2009–2020 breeding seasons from early February to mid-June. Seven study
 plots were established at elevations of 1,450–1,950 m. These plots were
 contiguously located and included ca. 560 ha, with each plot ca. 60–70 ha
 in size (Martin & Mouton, 2020). Collared and Masked Trogons were studied
 in the northern Andes in Yacambú
 National Park, a 269 km<sup>2</sup> area in Lara State,
 western Venezuela (9°38′N 69°40′W). The fieldwork was restricted to primary cloud forest habitat between 1400 and 2000 m, encompassing a similar elevation range to our study in Borneo. Data was collected during seven breeding seasons from 2002 to 2008 and from late February to early July. Research was conducted on seven study plots similar in size (ca. 60-70 ha) to those on the Borneo site (Martin and Mouton 2020). These trogons were not focal study species, such that we did not collect as comprehensive data as for the Whitehead’s Trogon. In general, the same standardized data collection methods were used in both Borneo and Venezuela studies, described as following. We located nests by observational cues of breeding pairs and systematic search (Martin & Geupel, 1993; Şahin Arslan & Martin, 2019; Şahin Arslan, Muñoz, & Martin, 2023), and measured the nest and nest-substrate heights using clinometers. We obtained the elevation of the nest location with a GPS device (Garmin, Olathe, Kansas, USA) for Whitehead’s Trogon. A nest initiation date was specified as the day the first egg was laid in a nest, and the egg-laying season was characterized by the distribution of nest initiation dates. Nests were checked daily during egg-laying and the first two days of incubation to obtain the exact day the last egg was laid to ascertain the start day of incubation. If a nest was found during incubation and was of unknown age, we checked the nest daily until hatch. Nests were also checked daily or twice daily near hatching and fledging to obtain exact timing of transitions for measuring incubation and nestling period lengths (Martin, Oteyza, Boyce, Lloyd, & Ton, 2015; Martin, Oteyza, Mitchell, Potticary, & Lloyd, 2015; Şahin Arslan et al., 2023). Otherwise, nests were generally checked every other day in Borneo, but from 1-4 days in Venezuela, to determine status and predation (Martin & Geupel, 1993). Clutch size was only used from nests located during building or egg-laying. We did not include nests observed later to ensure no partial loss was included (Martin et al., 2006). The incubation period was defined as the number of days between the last egg laid and last egg hatched (Martin, Auer, Bassar, Niklison, & Lloyd, 2007; Nice, 1954). The nestling period was defined as the days between the last egg hatched and the last nestling fledged and only used for nests where the last egg laid and hatch days were observed within 24 h of precision (Martin, Lloyd, et al., 2011). Daily nest predation rates and daily survival rates were estimated using maximum likelihood estimation via the Mayfield method (Hensler & Nichols, 1981; Mayfield, 1961, 1975). This method is highly correlated with the logistic exposure method (Şahin Arslan & Martin, 2023; Shaffer, 2004) but allows more ready comparisons with the wider availability of Mayfield estimates in the literature. We considered a nest successful if parents were observed feeding young outside the nest or the young left within two days of normal fledging age. If nest contents disappeared earlier, we considered it to be due to predation. We used an electronic scale with 0.001 g accuracy (ACCULAB, Elk Grove, Illinois, USA) to weigh fresh eggs on the day the last egg was laid or within the first 2 d of incubation. Nestlings were weighed for the first 3 days and then every other day throughout the rest of the nestling period, while also measuring wing chord and tarsus length using calipers (Mitutoyo) with an accuracy of 0.01 mm. As a part of a banding program, some adults were captured using mist-nets, and their mass, wing chord and tarsus lengths were measured. Parental behavior at nests was recorded using video cameras for Whitehead’s Trogon during both incubation and nestling stages starting near sunrise. We put 30x zoom video-cameras 4–10 m from the nests and camouflaged the cameras to prevent possible disturbance. We generally sought 6 h video recordings of parental behavior at a nest, but they varied from 4–9 h each day of video recording (mean duration during incubation = 5.96 + 0.24 h, <em>N = </em>27; during nestling period = 6.33 + 0.13 h, <em>N =</em> 97). Parental activity of the two trogon species in Venezuela were not video-recorded. Video recordings were used to quantify incubation nest attentiveness, as well as brooding attentiveness and feeding rates during the nestling period (Martin, Oteyza, Boyce, et al., 2015; Martin, Oteyza, Mitchell, et al., 2015; Şahin Arslan & Martin, 2019). Incubation nest attentiveness was measured as the percent of total video time that a parent sat on the eggs for each day of video recording (Martin, Oteyza, Boyce, et al., 2015). Brooding attentiveness for nestlings was calculated as the percent of video time that a parent sat on the nestlings for each day of video-recording, and feeding rates as the number of feeding trips of both parents to the nest<sup>-h </sup>for that recording. Statistics We conducted all analyses in R.4.2.2 (R Core Team 2022) and we present mean values with standard errors, ranges, and sample sizes. We estimated growth rate constants (K) for mass, tarsus length, and wing chord using the logistic growth model (Remeš & Martin, 2002). The model is based on the equation: W(t) = <em>A</em>/1 + e (−<em>K</em>∗(t−<em>t<sub>i</sub></em>)), where W(t) is body mass, tarsus length, or wing chord length, <em>A</em> is the asymptotic size, t is age and<em> t<sub>i</sub> </em>is the age at the inflection point where growth rate changes from accelerating to decelerating, and <em>K</em> is the maximum rate of growth which is obtained at the inflection point (Martin, 2015). We tested for differences in the growth curves between Whitehead’s and Collared Trogons using the nls function in R, and using nest identity as a random effect, while specifying the above equation and running a model for each species and then testing for model differences between species using anova. We used generalized linear mixed-effects models through the glmer function in the <em>lme4 </em>package (Bates, Mächler, Bolker, & Walker, 2015) to investigate the fixed effect of nestling age and brood size on feeding rate, with nest identity as a random effect. Brooding behavior changed in a backwards logistic curve (Şahin Arslan et al., 2023) and is described by the same three parameters as for growth rate above, where in this case <em>A </em>= asymptote at hatching day, <em>K </em>= instantaneous rate of change at the inflection time point, <em>t </em>= the inflection time point where the curve changes from accelerating to decelerating. We used the SSlogis function in the <em>nlme</em> package (Pinheiro & Bates, 2023) to describe the relationship and test for differences between brood sizes in slope (<em>K</em>), intercept (<em>A</em>), and inflection time point (<em>t</em>) of brooding behavior by Whitehead’s Trogon while using nest identity as a random effect. P ≤ 0.05 was considered as statistically significant throughout.
description: # Data from: Comparative reproductive ecology of Old and New World
 Trogons, an order in decline across the world
 [https://doi.org/10.5061/dryad.hx3ffbgmg](https://doi.org/10.5061/dryad.hx3ffbgmg) ## Description of the data and file structure #### WHTR INC Attentiveness.csv Incubation attentiveness video data for Whitehead's Trogon. Variables are as follows: NID = Nest ID Date = Date on which the nest was filmed. Day = Day after start of incubation (start of incubation is day 0 on the day the last egg was laid). Duration = duration in hours of the total video time at that nest on that Day Sum_On = duration in hours of the total time an adult was on the nest incubating during the video Percent_On = percent of the total daily video time (Duration) an adult was on the nest incubating. #### WHTRBRDTFEED.csv Video data of parental feeding and brooding behavior for Whitehead's Trogon. Variables are as follows: NID = Nest ID Date = Date on which the nest was filmed. Brood_Size = Number of nestlings when the nest was filmed. Day = Day after hatching (hatching is day 0) - age of nestlings. Duration = duration in hours of the total video time at that nest on that Day Sum_On = duration in hours of the total time an adult was on the nest brooding young during the video Percent_On = percent of the total daily video time (Duration) an adult was on the nest incubating. Feed = Total numbers of feeding trips to the nest divided by Duration to give trips per hour. #### WHTR\_COTR\_Nestling.csv Growth data for nestlings of Whitehead's (WHTR) and Collared (COTR) Trogons. Variables are as follows: NID = Nest ID SPP = Species studied, where WHTR = Whitehead's Trogon and COTR = Collared Trogon Day = Day after hatching (hatching is day 0) - age of nestlings. Mass = mass of each young on that Day(g) Tarsus = Tarsus length of each young on that Day (mm) Wing_Chord = Length of the wing chord for each young on that Day (mm) #### Trogon nest data.csv Clutch size, nesting initiation date, exposure days, nest success, and nest height of Whitehead's (WHTR), Collared (COTR), and Masked (MATR) Trogons. Variables are as follows: Site = Study site, either Malaysia or Venezuela. NID = Nest ID SPP = Species studied, where WHTR = Whitehead's Trogon, COTR = Collared Trogon, and MATR = Masked Trogon Clutch_Size = Number of eggs laid. Initiation_Date = date on which the first egg was laid Inc_exposure_days = Number of days the nest was observed with eggs Incubation_Fate = Fate of the nest during incubation, described as successful (eggs hatched), depredated (eated by a predator), Failed Due to Environmental Factors (e.g., tree falls down), and Nest Occupied, Monitoring Discontinued (monitoring discontinued due to end of the work for that season) Nestling_exposure_days = Number of days the nest was observed with nestlings Nestling_Fate = Fate of the nest during the nestling period, described as successful (young fledged), depredated (eated by a predator), Failed Due to Environmental Factors (e.g., tree falls down), Failed due to nestling mortality, and Nest Occupied, Monitoring Discontinued (monitoring discontinued due to end of the work for that season) Total_exposure_days = Total number of days the nest was observed with eggs or nestlings, including the egg-laying period over the entire nest period from first egg laid to fledging or failure. Final_Nest_Fate = Final fate of the nest over the entire nest period from first egg laid to fledging or failure, described as successful (young fledged), depredated (eated by a predator), Failed Due to Environmental Factors (e.g., tree falls down), Failed due to nestling mortality, and Nest Occupied, Monitoring Discontinued (monitoring discontinued due to end of the work for that season) Nest_Substrate_Height = Height of the substrate in which the nest was placed (m) Nest_Height = Height of the nest off the ground (m)