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Habitat loss and fragmentation affect forest birds through direct loss of breeding habitats, detrimental edge effects such as increased nest predation and brood parasitism, and possibly by limiting movements among remaining forest patches. Despite indirect evidence suggesting that landscape-scale bird movements are constrained by open areas, skepticism remains because birds routinely cross inhospitable terrain during migration. Here, we report evidence from 201 independent homing trials showing that landscape composition and configuration influence the movements (1-4 km) of two neotropical migrant (Black-throated Blue Warbler, Dendroica caerulescens and the Ovenbird, Seiurus aurocapillus) and one resident (Black-capped Chickadee, Poecile atricapillus) forest bird species in Quebec, Canada. Trials consisted of translocating territorial, mated males and measuring the time they needed to return to their territories (homing time), as well as the probability with which they returned to their territories within 30 h (homing success). Birds took more time and were less likely to return to their territories as forest cover decreased in the landscape. Once the simple linear variation due to forest cover was removed from landscape configuration variables, their influence on homing time and success was nonexistent or subtle, suggesting that landscape composition has greater predictive value than landscape configuration to infer constraints on forest bird movements. Indeed, and contrary to our expectation, mean nearest-neighbor distance between forest patches had no impact on homing time or success, but its coefficient of variation was positively correlated with homing time and negatively correlated with homing success. On the other hand, homing time and success were not influenced by the number of forest patches or the amount of edge per unit of forest cover. These results were consistent for all three bird species that we studied. Our data support the hypothesis that movements are constrained when forest birds travel in deforested and fragmented landscapes outside migratory periods. Such an impediment is likely to disrupt habitat selection processes, reduce the colonization of isolated forest patches, and ultimately, alter population structure and dynamics. Key words: agricultural landscape; Black-capped Chickadee; Black-throated Blue Warbler; connectivity; corridor; dispersal; forest cover; fragmentation; habitat loss; movement; Ovenbird.

Pinyon Jays (Gymnorhinus cyanocephalus) live in permanent flocks of 50-500 individuals on apparently undefended home ranges. We present date collected from 1973 to 1982 on the movement of individuals into and out of a color-banded flock. We banded 681 wanderers from other flocks, 46 of whom immigrated and bred in the study flock. Three hundred and eighty-three juveniles and yearlings born in the study flock disappeared from the natal flock; 22 of these bred in a neighboring flock. One was collected in 1973 as a yearling 600 km from its place of birth. Most dispersal occurred in the fall, but yearling females also dispersed during the breeding seasons. Fall dispersal was primarily by juveniles and included males and females in equal abundance. Females transferred between neighboring flocks more often than males. Many males returned to their natal flocks after months of wandering. As a result, 89% of male yearlings, but only 48% of female yearlings, in the study flock were born there. Annual variability in dispersal by yearlings was correlated with sex ratio in their natal and neighboring flocks; females joined flocks with strongly male-biased sex ratios and females left flocks with female-biased sex ratios. Low status of juveniles and yearlings, especially females, may explain why some dispersal occurred each year regardless of the sex ratio of the flock. Homing ability and the number of relatives in a flock were only weakly related to the percentage of yearlings and juveniles emigrating. Five consequences of dispersal were: (1) flock members may become familiar with resources outside their home range; (2) the sex ratio of yearlings approaches 1:1, despite extreme and variable sex ratio biases among yearlings born in the flock; (3) in some years the yearling cohort is predominantly composed of immigrants and in other years natives predominate; (4) immigrants have fewer relatives in the flock than natives have; and (5) the effective population size ranges from 222 to 370 and includes breeders of a flock and breeders in neighboring flocks.

Recent research on the homing mechanisms of pigeons may soon shed light on the issue and initiate further studies on pigeon behavior. More data are pouring in which indicate the presence of a magnetic based receptor in some species. More experiments are also being conducted on the mechanism of light-dependent magnetic sensors. The rational behind the 'village effect' or the tendency to fly towards villages is still under debate.