Group Effects and Background Color Patterns Affect the Exploratory Behavior of Tree Sparrows

Abstract

Exploratory behavior serves the function of acquiring information when facing environmental uncertainty, thus plays an important role for animals living on patchy or ephemeral resources. Our study tested the hypothesis that exploratory behavior is affected by ecological factors associated with the risk of predation. We conducted experiments to examine exploration behavior of wild‐caught Eurasian tree sparrows (Passer montanus) under the influences of background color patterns (white or camouflaged) and group sizes (single vs. five sparrows). We further conducted two‐pattern choice experiments and offered sparrows backgrounds combining those two color patterns. In comparisons with single sparrows, flocking sparrows had shorter landing latencies, started exploring sand patches earlier, spent less total time on the ground before pecking at the first patch and nearly successfully located and pecked all patches. In contrast, sparrows responded nearly indifferently to the two single‐pattern backgrounds; yet when given a choice, sparrows still favored the camouflaged portion in the two‐pattern backgrounds and first landed more frequently there. Twice as many patches were left untouched on the two‐pattern backgrounds, mostly by single sparrows, than on both types of single‐pattern backgrounds. In tests of flocks, sparrows that first landed on the ground to initiate exploration had a higher chance to also first explore a sand patch than random expectation on single‐pattern backgrounds, but not necessarily on two‐pattern backgrounds. Our results demonstrate context‐specific effects of social exploration, suggest possible influence of individual variation and offer evidence for advantages of group living in situations where explorers have to cope with environmental uncertainty.

Is Foraging Time Limited During Winter? – A Feeding Experiment with Tree Sparrows Under Different Predation Risk

“…Tree Sparrows in an outdoor aviary study (Kuo et al. ) with 11‐h daylight period spent approximately 15–27% (depending on the experimental settings, e.g. group size, background pattern) of the total observation time (only morning hours) on the ground, that is exploring and feeding out of the shelter (Y.‐F.…”

Energy state affects exploratory behavior of tree sparrows in a group context under differential food-patch distributions

“…Our study was conducted from November 2008 to January 2009 in Tainan (22°59′N, 120°11′E), Taiwan, and used Eurasian tree sparrows Passer montanus (Linnaeus, 1758) for experiments. They are ground feeders and residents throughout the lowlands of Taiwan, commonly occurring in pastures, crop fields, parks, schools, and populated urban areas, and often form foraging flocks all year round and roost communally in winter [ 27 ].…”

“…Mosquitofish ( Gambusia holbrooki ) in exploring responded to the presence of conspecifics (facilitation) and cues of potential danger (inhibition) [ 26 ]. When given a choice, exploring tree sparrows ( Passer montanus ) preferred to land on a camouflaged rather than a more-exposed white background, suggesting a response to environmental features associated with predation risk [ 27 ]. Both cases demonstrate that exploratory behavior may be as much affected by predation risk as foraging [ 24 ].…”