The interplay of resource availability and parent foraging strategies on juvenile sparrow individual specialization

Temporal variation in resource availability, amplified by global change,
may have strong impacts on species breeding at temperate and high
latitudes that cue their reproduction to exploit seasonal resource pulses.
This study examines how resource availability and parental care influence
niche partitioning between and within age classes in the rufous-collared
sparrow, which provides extensive parental care. We hypothesized juveniles
would exhibit narrower niches focused on high-quality resources compared
to adults, regardless of resource availability. We used stable isotope
analysis to quantify individual and population niches in juveniles and
adults across the breeding season in two cohorts experiencing contrasting
resource landscapes. Contrary to our initial hypothesis, juveniles
exhibited greater among individual diet variation and smaller total niche
widths (i.e., higher levels of individual specialization) during periods
of high food availability in comparison to periods of food scarcity.
Interestingly, total niche width and individual specialization of adults
remained stable across seasons despite a shift in trophic level,
highlighting their potential role in providing a consistent diet for their
young. These findings reveal a dynamic interplay between resource
availability, parental care, and individual specialization, with important
implications for understanding population resilience under variable
resource scenarios. The study also suggests that adult sparrows modify
their provisioning strategies based on resources, potentially buffering
offspring from environmental fluctuations. Understanding age-specific
responses to resource variation is crucial for predicting species
responses to ecological conditions, particularly in regions like central
Chile where seasonal resource limitation is expected to become more
variable in response to climate change.