DOI: 10.5061/dryad.6q573n606
title: Raw data set of pigeon body mass measurements

description: 1. Animal-borne logging devices are now commonly used to record and
 monitor the movements, physiology and behaviours of free-living animals.
 It is imperative that the impacts these devices have on the animals
 themselves is minimised. 2. One important consideration is the interaction
 between the body mass of the animal, and the mass of the device. 3. Using
 captive homing pigeons, we demonstrate that birds lose the equivalent
 amount of body mass compared to that of the logging device attached. With
 our experiments, we calculated that the compensatory mass loss because of
 the logging device equates to a total loss of 1,140 kJ of energy to the
 bird, over the 25-day period. This equates to 32% per day of their total
 daily energy budget. 4. We suggest that practitioners of
 biologging give due consideration to the possibility of a
 device-induced decrease in body mass when making decisions regarding
 device size, and when considering the period of the time of the year at
 which devices are attached. 5. It appears, based on the results of the
 present study, that device attachment is likely to be most disruptive
 during periods of regulated mass change, especially when periods of mass
 gain precede periods in which stored energy reserves are extensively
 utilised. 6. These findings have significant consequences for anyone using
 biologging technology on both wild and captive volant animals. Further
 studies utilising captive birds are now needed to fully understand how
 context- and species-dependent physiological responses to externally
 attached devices are.
description: <i>Birds
 and housing</i> A group of 18
 homing pigeons (hereonin referred to as pigeons) were housed at Royal
 Holloway University of London (Egham, UK). All birds were a minimum of 15
 months old and had lived together since hatching. The sex of the birds was
 a 55/45% split (males/females) (mean body mass at start of the study, 590
 ± 75.6 (<i>SD</i>) g). Birds were kept in a pigeon loft
 (dimensions 3.6 m (long), 2.4 m (wide)) with <i>ad libitum</i>
 access to food and water (see Portugal et al., 2017a; Portugal et al.
 2017b for further husbandry details). Wooden perches (n = 20) were
 attached to the sides of the loft, in arrangements of six perches in
 horizontal rows at three heights (1 m, 1.30 m, 1.60 m), plus two
 additional single perches (1.30 m). <i>Body
 mass measurements and artificial mass attachment</i> Birds were
 weighed twice weekly for four weeks, by being placed in a cotton bag and
 weighed using digital scales (0.1 g accuracy, Scales and Balances,
 Thetford, UK), before each pigeon was fitted with artificial mass in week
 five. The artificial devices mimicked the size and mass of typical logging
 devices <b>(</b>30 g, 3.7 x 2.4 x 0.8 cm), both those that are
 generally used for studies with birds and those which have been used
 previously with homing pigeons [Usherwood et al. 2014; Pettit et al. 2016;
 Taylor et al. 2019]. The artificial
 mass was attached to the back of the pigeons using Velcro strips and epoxy
 glue (total package mass 30 – 31 g, 5% of the mean body mass of the pigeon
 group at start of the study; see Sankey and Portugal (2019) and Sankey et
 al. (2021) for further details on logger attachment to the pigeons). Birds
 were then weighed twice weekly for the next 18 days (see Figure 1). On day
 18 the artificial loggers were removed, and birds were again weighed twice
 weekly for a four-week period. Following the four-week period, 10 birds
 were randomly selected to have the artificial loggers reattached, with the
 remaining 8 birds having no devices attached. All birds were then weighed
 twice weekly for a further 21 days (Figure 1). <i>Statistical analysis</i> Data were analysed using linear mixed models implemented in the lme4 [Bates et al. 2015] package of R v3.2.2 [R Core Team 2016]. The significance of random effects in mixed models was determined using likelihood ratio tests, and the significance of fixed effects in mixed models was determined using <i>t</i>-tests with Satterthwaite approximations to degrees of freedom implemented in the lmerTest package [Kuznetsova et al. 2016]. The model included a random intercept for individual identity and a random slope for the effect of time, which varied among measurement blocks. Data for time and mass were mean centred and scaled to unit variance prior to analysis. Full statistical findings can found in Supporting Information: Statistical Outputs.