Food-hoarding and nest-building propensities are associated in a cavity-nesting bird

The underlying mechanisms connecting correlated behaviors in wild populations remain largely unknown. Food-caching behavior is a prime example of an adaptive, compulsive-like behavior with a strong underlying innate drive-it starts after early development and is critical for survival-and individuals of some species rigorously and continuously cache up to tens of thousands of individual food items each season. Another behavior whose base processes may share similar underlying innate drive is nest building, as it involves repeatedly bringing material to the nest site often in a fixed pattern. There are various hypotheses attempting to explain inter- and intra-specific variation in nest characteristics, traditionally considering fitness-related consequences of such variation. Apparent non-functional nest variation remains largely unexplored but may have an association with other innately driven behaviors unrelated to nest building but potentially associated via a shared mechanism, such as food caching. Here, we show that individual variation in food hoarding is associated with differences in nest size in mountain chickadees (Poecile gambeli): individuals that cache more food also build bigger nests. Both behaviors are highly repeatable within individual females, but variation in nest size does not seem to have fitness consequences in our system. This finding suggests a possible connection in which the properties of one adaptive behavior may spillover and influence the outcome of another more neutral behavior, likely controlled by the same general underlying mechanism. Significance statement Food storing and some aspects of nest-building behavior are highly repetitive actions that appear compulsive-like in nature. We show that these two behaviors are correlated in a wild avian food-caching species, the mountain chickadee: individual females in a wild population that cache more food also build larger nests. Both behaviors were highly repeatable within individual birds across time and climatic condition. Food storing is highly adaptive in chickadees, whereas nest size appears to have little effect on offspring fitness in this system. Therefore, our data suggest that these two compulsive-like behaviors may be controlled by the same general mechanism and the strong innate drive of adaptive food caching may spillover to potentially impact neutral nest building.

Automated summary

The underlying mechanisms connecting correlated behaviors in wild populations, such as food caching and nest building, remain largely unknown. This study shows that in mountain chickadees, individual females that cache more food also build larger nests. These findings suggest that the innate drive of adaptive food caching may spillover and influence the outcome of neutral nest building.