Latitudinal Variation in the Timing of Nest Predator Activity Is Habitat Specific

Abstract

Aim

The goal of this work was to investigate whether the community of avian nest predators shifts from nocturnal to diurnal with changes in latitude. This hypothesis was formulated 70 years ago, under the rationale that longer day length during the bird breeding season at high latitudes increases opportunities for visual predators. Based on other studies investigating the identity of nest predators, we also considered variation in the habitat and nest height.

Location

Global.

Time Period

1994–2020.

Major Taxa Studied

Birds and their nest predators.

Methods

We reviewed studies that report the results of nest monitoring by video or photograph camera and collected data on the identity of nest predators. We then used the activity pattern of the predator species as a proxy to estimate whether predation events were nocturnal or diurnal. We used multivariate logistic and ordinal regressions to investigate whether the probability that nest predators are nocturnal changes with latitude and habitat.

Results

We found that both habitat and latitude explain variation in the circadian type of nest predators. In open habitats, nest predation was more often due to diurnal predators at high latitudes and nocturnal predators near the equator. In forests, on the other hand, nocturnal predator activity patterns were more common closer to the poles.

Main Conclusions

Using meta-analytical methods, we show that predator activity varies across habitats and latitude leading to markedly different consequences of predation for prey. These findings suggest that small-scale environmental factors such as habitat type can strongly affect and even neutralise larger-scale, ecological patterns. We speculate that day length might act along with other biotic and abiotic factors to shape the timing of nest predation in birds.