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The Social Miracle of Birds: How Do Mixed Foraging Groups Form?
In nature, birds exhibit a variety of social behaviors, the most striking of which are mixed foraging groups. This phenomenon not only reflects the interactions between birds, but also shows the strategies they adopt when facing survival challenges. Mixed foraging groups, or mixed foraging parties, usually consist of different species of insectivorous birds that move together while foraging. How exactly does this happen? Is it out of survival instinct or some kind of social need?
Composition of mixed foraging groups
Mixed foraging groups often form around a so-called "core species". Research shows that these core species not only help inspire the formation of mixed foraging groups but also maintain cohesion among different bird species. Their influence in the group is often greater than that of other species. Core species often share some common characteristics, such as adopting general foraging strategies and social behaviors.
Species often called "chaperones" or "travelers" that follow only after a mixed foraging herd enters their territory. These species often gain better fitness after participating in mixed foraging groups.
In addition to core species, there are also "sentinel" species present in mixed foraging groups. Unlike core species, these sentinel birds mainly hunt flying insects and do not often form groups. Their main role is to alert other birds to guard against incoming predators.
Benefits and costs of mixed foraging groups
Although the formation of mixed foraging groups represents a cooperative relationship between birds, this does not mean that all birds benefit from it. Ecologists generally believe that species with similar ecological niches compete for resources, but mixed foraging groups show that some birds choose to cooperate to obtain more food during coexistence. This is particularly evident in their ability to more efficiently detect food sources, avoid areas that have already been foraged, and drive insects out of hiding areas.
Other studies have shown that joining mixed foraging groups can reduce the risk of predation. When a bird is surrounded by other birds, it is less likely to be targeted by predators.
However, mixed foraging groups are not without costs. Some birds may be forced out of optimal feeding areas in order to follow mixed foraging flocks toward areas of environmental disadvantage. Additionally, other birds may need to change their foraging strategies to conform to the group's behavior.
Phenomena in the Northern Hemisphere
In temperate regions of the Northern Hemisphere, mixed foraging groups are usually led by members of the family Paridae, and are later joined by insectivorous birds such as tree woodpeckers, tree snails, and crested kings. This behavior is especially common outside of the breeding season. Although the advantages of this behavior are unclear, there is evidence that it provides some degree of cover for duller birds such as forest garlands or woodpeckers.
Phenomena in tropical places
In the tropics, especially in the neotropical crocodile trees, mixed feeding groups of insects reach the peak of their development. The core members of these mixed foraging groups may be black-throated tiger swallows or three-striped finches. Such core species often have striking plumage colors that encourage other birds to flock to them. Although these core species are well known, it is not necessarily the case that such species are the initiators of mixed foraging groups.
In one observed example, a specific bottom-throat current was lingering around among a group of foraging birds. However, this bird did not mainly fly to catch food, so it seemed that it only encountered it by chance. No active group behavior was initiated.
Phenomena in the tropics of the Old World
Mixed foraging groups in the Old World tend to be more loosely formed than in the Neotropics, with many remaining together only during the activity of a core species. Particularly in tropical Asia, mixed foraging flocks such as Sri Lanka can reach the point where hundreds of birds move together throughout the day. In these places, core species such as the orange-billed stork are accompanied by other birds such as the Asian little mockingbird or geranium. This phenomenon is also seen in African rainforests, where core species include ring-necked beetles and sunrise birds, often attracting other species.
Based on the above observations, it is not difficult to find that the diversity of bird social behaviors and ecological interactions are full of surprises and revelations. When facing the dangerous environment of nature, the formation and operation of mixed foraging groups are not only survival strategies, but also demonstrate a profound social behavior. Regarding these wonderful evolutionary phenomena, have you ever thought about what unexpected effects they may have in nature?
