Positive Interactions among Foraging Seabirds, Marine Mammals and Fishes and Implications for Their Conservation

Abstract

There is increasing recognition of the importance of "positive interactions" among species in structuring communities. For seabirds, an important kind of positive interaction is the use of birds of the same species, birds of other species, and other marine predators such as cetaceans, seals and fishes as cues to the presence of prey. The process by which a single bird uses, say, a feeding flock of birds as a cue to the presence of prey is called "local enhancement" or "facilitation." There are subtly different uses of each of these terms, but the issue we address here is the ubiquity of positive interactions between seabirds and other marine predators when foraging at sea, and whether as a result of their associations the feeding success, and therefore presumably the fitness, of individual seabirds is increased. If this contention is true, then it implies that conservation of any one species of seabird must take into consideration the status and possible conservation of those species that the focal species uses as a cue while foraging. For example, conservation of great shearwaters (Ardenna gravis), which often feed over tuna (e.g., Thunnus) schools, should take in to consideration conservation of tuna. Ecosystem management depends on understanding the importance of such processes; the loss of biodiversity, and the consequent threat to foraging success, may be a substantial threat to the stability of marine ecosystems.

Spatial ecology of long‐tailed ducks and white‐winged scoters wintering on Nantucket Shoals

“…This previously undescribed association suggests a role of local enhancement in the formation and maintenance of winter feeding aggregations of seabirds (Fauchald 2009, Veit and Harrison 2017. This previously undescribed association suggests a role of local enhancement in the formation and maintenance of winter feeding aggregations of seabirds (Fauchald 2009, Veit and Harrison 2017.…”

“…Thus, both long-tailed ducks and white-winged scoters could profitably use the locations of aggregations of the other species as reliable indicators of good feeding areas to improve foraging efficiency. We do not know the exact reason for the statistical association between these two species of sea ducks, but the association seems unlikely to be coincidental, as the use of local enhancement by seabirds to find prey has been extensively documented (Fauchald 2009, Veit andHarrison 2017). The white-winged scoter population is seasonally permanent with no evidence of a commute (Video S1) or nocturnal foraging behavior (Lewis et al 2005), and their extensive distribution may serve as a highly visible navigational cue to feeding areas for commuting long-tailed ducks to Nantucket Shoals from nighttime roosts on Nantucket Sound (White et al 2009; Fig.…”

“…For example, longtailed ducks off Massachusetts declined from highs of nearly half a million birds in~1990-2010 to less than a tenth of those in 2017-2018 (National Audubon Society 2010). Sociality may function to drive flock formation and to enhance resource location (Hein et al 2015, Veit and Harrison 2017, Berdahl et al 2018, Zou et al 2018). 1; Video S1).…”

Commensal association of the common kingfisher with foraging Eurasian otters

“…Positive interactions amongst species are widespread in nature (Bronstein, ). In a foraging context, these interactions may consist of local enhancement, when an individual uses cues from individuals of another species to locate food, or facilitation when food is made more readily available by the individuals of other species (Veit & Harrison, ). Facilitation may evolve as mutualism when it is reciprocally beneficial, as commensalism when the facilitator is neither benefited nor harmed or as parasitism when the host is used as a resource and harmed (Bronstein, , ).…”

“…A widespread commensal feeding association is that between birds and large grazing herbivores that flush or expose prey such as insects on which the following birds can opportunistically feed (reviewed by Dean and Macdonald ()). Other classical examples include associations between kites and foraging monkeys (Fontaine, ), seabirds and feeding marine mammals (Thiebot & Weimerskirch, ; Veit & Harrison, ) or birds following foraging honey badgers Mellivora capensis in southern Africa: honey badgers are powerful diggers and flush rodents or reptiles from their underground refuges, providing foraging opportunities to predatory birds such as pale‐chanting goshawks Melierax canorus (Paxton 1988). In mutualistic associations, both parties benefit from the association, such as in the case of cleaning associations, in which birds remove ectoparasites and other food material from their mammal hosts (Sazima, Jordan, Guimaraes, Reis, & Sazima, ).…”