DOI: 10.5061/dryad.xd2547dh9
title: Rapid recovery by fat- and muscle-depleted Blackpoll Warblers following trans-oceanic migration is driven by time-minimization

description: Non-stop endurance flights are a defining characteristic of many
 long-distance migratory birds but subsequent recovery phases are not
 typically distinguished from fueling phases (collectively ‘stopovers’),
 despite endurance flights inducing marked physiological changes including
 flight muscle atrophy and gastrointestinal tract reductions. Here, we
 hypothesize that recovery requires unique behavioral adaptations, leading
 to departures from the predictions of optimal migration theory for
 time-minimizing migrants. We predict that recovering birds will 1) select
 (moist) food-rich habitats on arrival; 2) have slow initial fueling rates
 due to decreased gastrointestinal capacity; 3) show a negative correlation
 between stopover duration and arrival condition instead of a negative
 correlation with fuel deposition rate (FDR); 4) stopover longer than
 required to store energy reserves for subsequent flights; and 5) show
 evidence of rebuilding flight muscles. To test these predictions, we
 studied Blackpoll Warblers Setophaga striata in northern Colombia
 following trans-oceanic flights &gt;2250 km. Birds selected dry
 seasonal habitats, despite proximity of moist forests, and among 1227
 captured individuals, 14-21% were emaciated and 88% had atrophied flight
 muscles. We recaptured 74 individuals, revealing net positive mass gains
 and, contrary to Prediction 2, no evidence for slow initial recovery
 rates. Contrary to Prediction 3, stopover duration was only weakly
 correlated with arrival condition and birds with high FDR (4.9% LBM/day)
 had shorter durations (3 days) relative to birds with slower rates (7
 days) - both groups accumulated sufficient fuel to reach non-breeding
 (over-wintering) grounds 500-1000 km away. Mass increases were largely
 attributable to fat deposition but some birds improved flight muscle
 condition (31.9%), consistent with Prediction 5. Together these results
 reveal a strong selection for time-minimization in the decisions made by
 Blackpoll Warblers following trans-oceanic flights, likely mediated
 through advantages to early arrival on non-breeding grounds, contrary to
 our hypothesis of recovery imposing unique selection pressures.
description: This dataset consists of data collected using two
 methods: 1. Occupancy surveys carried out between
 September-November in 2016 (northern Colombia) and 2017 (Panama) across 21
 study sites with associated vegetation data. For the data presented here,
 5748 repetitions of 264 individual transects were used, where each
 transect was 100 m long and surveyed during 10 minutes. An average of four
 repeat visits were made to each transect every 10 days during six 10-day
 periods between September and November. These data have been processed to
 create an observation history for Blackpoll Warblers in each transect,
 along with associated vegetation and climatic data for each.
 2. A constant effort mist-netting station was established in the
 El Pantano reserve on the Guajira Peninsula of Colombia during two fall
 migrations. Mist-nets were opened daily between 6 am and 11 am and
 captured birds were banded and data were taken on species, age, sex,
 physical condition, wing and weight. Data included here only include
 captures of Blackpoll Warblers the focal species of the study. Subsequent
 processing was carried out to model body mass change in recaptured birds
 and stopover durations (see methods in original article).
description: Missing values are either represented by NA or a blank cell in
 columns when NA is not accepted by Dryad.