10.5061/DRYAD.QZ612JMDM
DeSimone, Joely
0000-0002-7486-6443
University of Montana
Tobalske, Bret W
University of Montana
Breuner, Creagh W
University of Montana
Physiology and behavior under food limitation support an escape, not
preparative, response in the nomadic Pine Siskin (Spinus pinus)
Dryad
dataset
2021
body composition
irruption
locomotor activity
pine siskin
FOS: Biological sciences
2021-02-08T00:00:00Z
2021-02-08T00:00:00Z
en
156820 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Migration allows animals to use resources that are variable in time and/or
space, with different migratory strategies depending on the predictability
of resource variation. When food varies seasonally, obligate migrants
anticipate and prepare for migration. In contrast, facultative migrants,
whose movements are unpredictable in timing and destination, may either
prepare for migration or escape when resources are depleted. We propose
and test two alternative hypotheses regarding the behavioral and
physiological responses of facultative migrants to declining food
availability. (1) The Prepare Hypothesis predicts that facultative
migrants prepare for departure by increasing fuel stores in response to
declining food availability, and elevations of baseline corticosterone
(CORT) facilitate increased activity. (2) The Escape Hypothesis predicts
that facultative migrants do not prepare for departure, body condition
declines as food availability declines, and stress-induced levels of CORT
induce escape behavior when both energetic condition and food resources
are low. We conducted a 16-day experiment, measuring body composition
(using Quantitative Magnetic Resonance), activity (using force perches),
and baseline CORT in Pine Siskins (Spinus pinus) given ad libitum food or
a slow decline, fast decline, or randomly changing amount of food. Our
results support the Escape Hypothesis: body condition declined as food
declined, decreases in body and fat mass were associated with increases in
baseline CORT, and activity increased only when food availability was low.
This work suggests that facultative migration in autumn allows birds to
escape low resource areas and that the underlying physiological mechanisms
differ from those driving both seasonal, obligate migrations and spring
nomadic movements.
physiology_data.csv contains food availability, mass, body composition,
and CORT data for each individual over the course of the experiment
activity_data.csv contains hopping activity for each individual, for every
daylight hour of every experimental day