PARENT SESSION
Contributed Oral Session 18: Avian Communities and Populations
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal

Measuring the large-scale, gap-crossing decision rules of Black-capped Chickadees: A translocation experiment.

Belisle, Marc^*,1, Fontaine, Marie-Claude¹, ¹ Departement de biologie, Sherbrooke, Quebec, Canada

ABSTRACT- The propensity with which a forest bird will move to forest patches located > 250 m from all forest edges has so far not been quantified. We addressed this problem by translocating wintering Black-capped Chickadees (Poecile atricapilla; 1 bird/trial) into 3 isolated, focal patches of forest. The nearest forest edges to these focal patches were 100 m, 180 m and 800 m, respectively. The focal patches were small enough (< 0.1 ha) to keep track of the birds and to assume that individuals visually perceived all surrounding forest patches. We recorded the time elapsed before birds left the focal patches as well as the exact location where birds entered forest cover after leaving the focal patches. We expected that chickadees translocated to highly isolated, focal patches to be more reluctant to travel into open habitat. Hence, chickadees translocated into highly isolated, focal patches should spend more time into focal patches and be more likely to fly to the nearest forest edge available. We performed the translocations within three agricultural landscapes surrounding Sherbrooke, Quebec, in winter 2005. So far, 50 individuals were translocated in each treatment/landscape. As expected, the more isolated the focal patch was, the longer chickadees took before leaving it. Yet, the difference between the 100 m and the 180 m patches was marginal (few seconds) compared to the most isolated patch (several minutes), suggesting that a threshold distance might be involved. Moreover, most individuals translocated into the 100 m and 180 m treatments flew to the closest forest edge available. On the other hand, most birds released into 800 m treatment did not choose the closest forest edge available. We will contrast the observed distances traveled to the frequency distribution of forest edges available to the chickadees in order to investigate further why this observation did not follow our prediction. This is the first experiment to directly quantify the reluctance of forest birds to cross large open areas. This information is needed to estimate the visitation rate of isolated forest patches that can have strong leverage on the predictions of demographic models.

Key words: movement, habitat fragmentation, translocation experiment, gap-crossing rules