Deep learning analysis of nest camera video recordings reveals temperature-sensitive incubation behavior in the purple martin (Progne subis)

Abstract

Incubation is a key life history stage for birds, and incubation attentiveness can have significant fitness consequences for both parents and offspring. Incubation is, however, a challenging phenomenon to observe and studies generally either measure some proxy of the target behavior, or risk disturbing birds through direct observation. More recently, nest cameras have provided a non-intrusive way to directly observe incubation, but analysis of these data is time-consuming. Here, we use the results of the first deep learning model which automated analysis of nest camera video recordings from eight purple martin (Progne subis) nests over the entire incubation period at a 1-s resolution. We mathematically define the initiation of incubation, characterize the change in nest attentiveness during incubation, and analyze the factors determining nest attentiveness and on- and off-bout duration during the incubation process. A random forest regression model identified the most important predictors of nest attentiveness. Attentiveness decreased with increasing temperature, but the strength of this response increased above the presumed physiological zero egg temperature, below which egg development ceases. This implies that the purple martins are able to adjust their incubation behavior in a complex, multiple-state manner to an extrinsic stimulus. Our study highlights the value of high-resolution datasets created using artificial intelligence for the analysis of nest camera video recordings of animal behavior. The use of artificial intelligence for image classification tasks is becoming commonplace in society. This technology is beginning to be used to automate the analysis of video recordings of wildlife behavior. Here, we use the results of the first such classification from nest camera video recordings of the purple martin (Progne subis) to determine the factors affecting incubation attentiveness (the proportion of time that the adults spend in contact with eggs). Incubation attentiveness is important because it can affect hatch rate and have carry-over effects both for the condition of the incubating adults and the quality of the resulting offspring. Our analysis found that attentiveness was mainly affected by ambient temperature, with incubating adults reducing their efforts as ambient temperature reaches the minimum threshold for egg development.