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

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.     

Microhabitat use and hindwing phenotype in Hipparchia semele (Lepidoptera, Satyrinae): thermoregulation and background matching

Abstract. 1. Microhabitat use and background matching by adult Hipparchia semele (L.) in a coastal sand dune site in south Wales were studied during the flight period of 1986.
2. Microhabitat use by both sexes is related to temperature and activity. When settling substrates are cool, typically during the early morning, most individuals are located on the warmest basking substrate, lichen patches. After a period of warming, males perch to locate mates on exposed areas of sand where there is a large field of view and where they are visually apparent. Egg-laying females tend to settle on lichen patches throughout the day.
3. Overall, females are maximally visually cryptic when settled on lichen patches with unexposed forewings. Male crypsis on lichen is less effective, but greater on most other substrates, than that of females. It is argued that individuals match lichen patches because this substrate is used when they are most liable to detection and capture by vertebrate predators. Male crypsis is probably a compromise between maximizing protection on lichen patches and requirements for resemblance to other substrates.
4. The underside hindwing phenotype does not match sand. Background matching to this substrate is probably not important because it tends to be used when individuals are active and can effectively use secondary defence mechanisms.
5. It is suggested that the apical eyespot and orange patch on the forewing underside have a dual role in secondary defence, acting as a startling and deflective device, being exposed by disturbed individuals and by those engaged in activities which may disrupt the visual crypsis afforded by the hindwing underside.