Testing camera traps as a potential tool for detecting nest predation of birds in a tropical rainforest environment

Abstract

Identification of the predators of bird nests is essential to test ecological and evolutionary hypotheses and to make practical management decisions. A variety of nest monitoring devices have been proposed but many remain difficult to set up in the field. The aim of this study was to test camera traps as a potential tool to study predation of natural nests in a tropical rainforest environment. Specifically, we registered the predators, assessed their size range, and we compared the use of one and two cameras per nest. Of 122 nests from 24 bird species, 45 (37%) were depredated, and the cameras recorded the predator species in 29 of the total of depredated nests (64%). We identified predators in eight of 16 depredated nests (50%) in which we used one camera trap per nest, and we identified predators in 21 of 29 depredated nests (72%) when we used two camera traps per nest. The predators included six species of birds and six species of mammals, with body masses varying from 20 g to 16.5 kg. Causes for 10 of the 16 detection failures were identified and are discussed. These results suggest that camera traps are viable tools to investigate nest predation in a tropical rainforest area.

Bats as predators at the nests of tropical forest birds

“…A–D, Supplementary material Appendix 1 Video 1). We are confident that bats depredated the other nests because: 1) in all of the cases, videos confirmed that nests were active in the day before bats visited them, 2) all apparent predations were confirmed by nest checking in the following days, after only bats were detected in the cameras, 3) camera traps have been efficient in detecting nest predation by other animal species from the study area (Ribeiro‐Silva et al ), 4) in the cases in which nests contained eggs, these were the only depredated nests in which pieces of eggshells were left within the incubatory chamber, a pattern of evidence not associated with the other local nest predators (Zima et al unpubl.) and 5) in the nests of the black jacobin and of the Atlantic royal flycatcher, which contained eggs, the way bats positioned their heads toward the incubatory chambers suggest that they have disturbed and presumably consumed their contents at that place, once eggs might be difficult to be carried away.…”

“…Nests were monitored using digital camera traps Bushnell TrophyCam™, model 119437C (Bushnell Outdoor Products, Kansas, USA), that were installed 1–3 m away from each nest depending on the availability of adequate branches or saplings with which to tie them. The cameras were programmed to record 30 s videos, with Low infrared LED intensity, ‘High’ sensor level, intervals of 3 s between triggers (Ribeiro‐Silva et al ), and videos were stored on 2 or 16 GB memory cards. Cameras and nests were checked every 1–5 d, and recordings were analyzed in the laboratory.…”

“…For this reason, a substantial literature in avian ecology and evolution has addressed nest predation and nest predators. The main predators of bird nests have traditionally been identified as mammals, snakes, other birds, as well as invertebrates in some cases (Thompson III , Reidy and Thompson III , Menezes and Marini , Ribeiro‐Silva et al ). These predators typically locate nests using visual, olfactory or auditory cues, and bird's anti‐predatory strategies are presumed to reduce nest detectability via these cues (Skutch , Collias , Ibáñez‐Álamo et al ).…”

“…Despite the above predictions, the accurate identification of nest predators in many studies remains problematic (Ibáñez‐Álamo et al ). Lists of nest predator species are extensive (Menezes and Marini ), but they are mostly based on occasional records, and are biased towards diurnal predation events that are more detectable, whereas studies involving efficient continuous monitoring of nests are scarce (Reidy and Thompson III , Ribeiro‐Silva et al ). In a large‐scale nest monitoring study using infra‐red camera traps in a well‐preserved Atlantic Forest area, we reveal that bats are secretive brood predators.…”

Egg ejection cost can limit defence strategies against brood parasitism

“…Thus, nest predation should be primarily a daylight event. However, recent studies have shown that night predation also plays an important role in decreasing nest survival (Ribeiro‐Silva et al, ). Given low night luminosity, nocturnal predators are more likely to use olfactory (Mihailova, Berg, Buchanan, & Bennett, ; Whelan, Dilge, Robson, Hallyn, & Dilge, ), thermal (Stake, Thompson, Faaborg, & Burhans, ; Weatherhead & Blouin‐Demers, ) and auditory cues (Briskie, Martin, & Martin, ; Halupka, ; Rice, ) to find nests.…”