Data from: When do tropical birds breed? The case of Colombian species assemblages

Understanding when tropical birds breed is key to life-history theory and
to predicting how species will respond to environmental change. While
early views emphasized the potential for year-round breeding in the
tropics, accumulating evidence suggests that reproductive activity in most
tropical birds follows some degree of seasonality, often linked to
rainfall and associated food pulses. However, large-scale evaluations
across ecological gradients remain scarce. Here, we investigated the
breeding seasonality of Colombian resident birds using over 80,000 records
compiled from bird banding programs and the Global Biodiversity
Information Facility (GBIF). These data included birds in breeding
condition, active nests, nestlings, and adults displaying reproductive
behavior. We asked four main questions: (a) Do Colombian birds exhibit
seasonal breeding activity? (b) Does the degree of seasonality vary with
latitude and elevation? (c) Are there geographic differences
in breeding patterns across Colombia’s biogeographic regions? (d)
How does breeding activity vary among feeding guilds? We used time-series
analysis, circular statistics, and generalized additive models (GAMs) to
evaluate breeding patterns at national and regional levels, incorporating
geographic variables and trophic guild. We found a clear seasonal pattern
in breeding activity, with a main peak in April and low but consistent
activity throughout the year, especially in the Andes. Breeding was more
synchronized at higher latitudes and more extended near the Equator.
Elevation also shaped seasonality: lowland bird communities showed broader
breeding seasons, while mid- and high-elevation assemblages had narrower
windows, with peaks shifting toward mid-year. Regional and trophic
variation was also marked. Breeding generally coincided with the onset of
rains and avoided extreme dry or wet months. Our findings offer new
insights into tropical bird reproduction, showing that breeding
in Colombia follows clear seasonal patterns shaped by rainfall, elevation,
and diet, and highlighting the complexity of tropical phenology.