Annual Temperature Variation, Not Number of Predators, Predicts Variation in Foraging Group Size Among Pigeons Worldwide

TL;DR

Pigeon foraging group sizes are more influenced by annual temperature variation than by the number of predators, according to a global study.

Contribution

This study identifies annual temperature variation as a key driver of foraging group size in pigeons, challenging the traditional focus on predation.

Findings

Foraging group size increases with latitude and elevation in continental pigeon species.

Annual temperature variation is the strongest predictor of group size in continental pigeons.

Island pigeon species show smaller group sizes and no significant link to temperature variation.

Abstract

While species diversity and traits linked to reproduction and survival are known to vary with latitude, altitude, and island residency, much less is known about how behavioural traits change across broad biogeographical gradients. Using data from the literature, I investigated global variation in foraging group size within a large avian family—the pigeons. Specifically, I examined how group size is related to climatic factors and predator richness. Group size tended to increase at higher latitudes and elevations and was generally smaller among island species. The number of predators within a species’ breeding range showed no significant association with group size. Among climatic variables, annual temperature variation was the strongest predictor of group size, with greater variation linked to larger groups. These findings suggest that, at a global scale, climatic factors—rather than predation—play a primary role in shaping variation in foraging group size in pigeons.

Many life history traits show predictable patterns at broad biogeographical scales, yet much less is known about how behavioural traits vary across such gradients. In this study, I investigated global variation in foraging group size within a large, cosmopolitan avian family—the pigeons—and assessed the roles of climate and predation in shaping these patterns. I compiled data from the literature for species occurring across a range of latitudes, altitudes, and habitats (islands v. continents) and analyzed the data within a phylogenetic framework that accounted for both biogeographical and ecological drivers of group size. Foraging group size increased with latitude among continental species but did not follow these trends on islands, where groups were generally smaller. Group size also increased at higher elevations. Among the climatic variables examined, annual temperature variation emerged as the strongest latitudinal predictor: greater temperature variability was associated with larger group sizes in continental species, but not in island species. The number of predators within a species’ breeding range showed no significant relationship with group size. These findings suggest that climatic variability, rather than number of predators, is a key driver of foraging group size in pigeons at the biogeographical scale.

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