Unfamiliar stopover sites and the value of social information during migration

Abstract

The better informed an individual, the better able to meet the demands of a variable environment. When a migratory bird stops over during passage, it must adjust to unfamiliar surroundings, satisfy nutritional demands, compete with other migrants and resident birds for limited resources, avoid predation, balance conflicting demands between predator avoidance and food acquisition, and often cope with unfavorable weather. A successful migration depends on solving these and other problems, the solutions to which are measured in units of time and condition. Migrants that gather reliable information about unfamiliar habitats in a timely fashion increase the likelihood of a successful migration. For example, a migrant may estimate food availability or predator pressure faster and more accurately by combining personal information gathered while sampling with social information obtained while observing the behavior of other migrants. In this paper, we provide a brief review of information use in the context of migratory stopover, a subject that has received little attention, and present preliminary results of an ongoing field investigation of the use of social information by migrants. Focal sampling of free-ranging and radio-tagged Nearctic-Neotropical passerine migrants in coastal habitat following flight across the Gulf of Mexico suggests that migrants respond to a lack of information by foraging in temporary feeding assemblages. This preference for flock foraging declines over the course of the stopover period in insectivorous migrants but persists in omnivorous birds, which suggests that the value of social information depends, in part, on a migrant's foraging ecology. We argue that social foraging enables migrants to assess more fully unfamiliar environments during stopover, thereby reducing risks associated with lack of information.

Observation of Daytime Sleep-like Behavior in a Migratory Songbird during Stopover

“…Consequently, uniformly distributed arthropod prey promotes restricted space use and, potentially, the defense of temporary territories (Bibby andGreen 1980, Chernetsov 2012). Consistent with this notion, insectivorous migrants were found to decrease their propensity to forage in flocks the day after they arrived at a stopover site, while omnivorous migrants were just as likely to be found in flocks then as when they first arrived (Németh and Moore 2007). Making this distinction is useful when one would like to understand the source and the value of information used by refueling migrants.…”

“…Migration is associated with a set of ecological conditions under which social information should be favored when available. Migrating birds are under time and energetic constraints Lindström 1990, Alerstam andHedenström 1998), so any factor that causes a delay in refueling and departure from a stopover, including increased risk of predation Moore 1999, Cimprich et al 2005), inclement weather (Newton 2007), unfamiliar habitat (Németh and Moore 2007), and sleep loss (Fuchs et al 2006, 2009, Németh 2009) can be viewed as increasing the cost of information acquisition and should promote social information use in migrants.…”

“…Migrants often arrive at stopover sites with little or no information about local conditions, and start refueling only after an initial familiarization period Aborn 2000). During the transition from arrival to refueling and then to departure, the relative value of social versus personal information continuously changes (Németh and Moore 2007). Even if a migrant obtains reliable, personal sampling information about the distribution and quality of food resources at an unfamiliar stopover site, as the ecological context at a stopover site changes the once-accurate information becomes erroneous and outdated, leaving the migrant uncertain about the success of its decisions.…”

“…Novel environments increase the costs of collecting information (Dukas 1998). In a previous study (Németh and Moore 2007), we tested whether migrants relied more heavily on social information soon after arriving at a novel stopover site to compensate for the lack of prior information. We called this the Information Constraint Hypothesis.…”

Long-distance migrating species of birds travel in larger groups

“…Flocking while foraging has been shown to increase foraging efficiency and decrease predation risk [12], and may be particularly useful in stopover habitats that are at best visited only infrequently [13].…”