Bird mixed-flocks and nuclear species in a tecoma savanna in the Pantanal

Abstract

In bird mixed flocks, a prominent species, the so-called nuclear species, improves the cohesion and maintenance of the flocks, while other less conspicuous species are assumed as satellite. In this study we described the composition, as well as examined the existence of both nuclear and satellite species in mixed flocks of a savanna in the Pantanal. The observations were developed using three transects during the dry season of 2002. Bird species abundance and respective rate of participation in mixed flocks were surveyed by transects, while intraspecific sociality, communication, foraging maneuvers of species, and responses to predators were sampled by direct observations. These parameters were evaluated to distinguish nuclear from satellite species. We observed 41 bird mixed flocks, which included from 2 to 17 species of which Suiriri suiriri (Vieillot), one of the most abundant species, was present in most flocks, often represented by 2-4 individuals, whereas most other species occurred lone or in pairs. While foraging by acrobatic maneuvers S. suiriri often gave contact calls, as well as earlier giving alarm calls if faced with a risk of predation. In addition, S. suiriri always started mixed flocks movements. Conversely, most other species were silent and closely inspected the vegetation while foraging. Such species always followed S. suiriri and seldom gave contact calls. Hence, the conspicuous traits exhibited by S. suiriri, potentially, are exploited by the other bird species as cues, which are important references for bird mixed flock cohesion in a savanna in the southern Pantanal.Keywords: bird mixed flocks, nuclear species, Pantanal, Suiriri suiriri, social behavior. Bandos mistos de aves e espécie nuclear em uma savana de ipês no Pantanal ResumoEm bandos mistos de aves, a espécie nuclear possui características que promovem a coesão e manutenção dos bandos, enquanto espécies menos conspícuas são consideradas satélites. Este estudo teve como objetivos descrever a composição, bem como analisar a existência de espécies nucleares e satélites em bandos mistos em um tipo de savana do Pantanal Sul. As observações foram desenvolvidas ao longo de três trajetos durante a estação seca de 2002. A abundância das espécies e respectiva taxa de participação nos bandos mistos foram amostradas através de trajetos, enquanto dados sobre socialidade intra-específica, comunicação, manobras de forrageio e reação a predadores foram obtidos através de observações diretas. Esses parâmetros foram adotados como critérios, para distinguir espécies nucleares de satélites. Foram detectados 41 bandos mistos que incluíram de 2 a 17 espécies, sendo que Suiriri suiriri, uma das espécies mais abundantes na savana de ipês, esteve presente em praticamente todos os bandos, na forma de um par ou grupo de indivíduos que, regularmente, emitiam chamados de contato, enquanto forrageavam executando manobras acrobáticas. Também, emitiram chamados de alarme quando em risco de predação e foram seguidos pelas demais espécies durante os desloc...

Seasonal drivers of mixed-species flocks from tropical savannas: insights from the Pantanal wetland

“…In agreement with our results, Hutto (1994) and Gram (1998) suggested that the congeneric P. caerulea, a migratory species, plays an active nuclear role in flocks of a semi-deciduous dry forest in Mexico. Similar active behavior has been observed for other nuclear species such as the flycatcher Suiriri suiriri in our https://journal.afonet.org/vol94/iss3/art3/ study area (de Vasconcelos et al 2008), and in the southern Pantanal (Amaral and Ragusa-Netto 2008) during the dry season. However, we suggest that C. rufus, a flycatcher species, acts as a sentinel in flocks, however we have still not observed any situations involving alarm calls.…”

“…Bird richness in this ecosystem represents about 30% of the Brazilian avifauna, and species inhabit different ecological niches and types of vegetation (Sick 1997, Gwynne et al 2010. Birds also participate in mixed-species flocks through a gradient of grassy-shrubby-forest vegetation (Amaral and Ragusa-Netto 2008), which can also be strongly influenced by seasonal change in the hydrological cycle (de Pinho et al 2017). Moreover, the Pantanal comprises a natural mosaic of patchy forests, savannas, and grasslands, covered by water during the flood season (January to March), but more accessible during the dry (May to September) and the beginning of the rainy (October to April) season (Junk et al 2006, Alho 2008, Alho et al 2019.…”

Polyspecific associations of Cercopithecus campbelli and C. petaurista with C. diana: what are the costs and benefits?

“…I then provided data on predator presence as well as responses to predators and other stimuli to evaluate potential antipredator benefits of association with C. diana. I predicted that C. diana would most often be the first caller to harmful stimuli, as found in previous studies of C. diana and other nuclear species (Bshary and Noë 1997a;Amaral and Ragusa-Netto 2008).…”

“…Bird species that promote the formation and maintenance of mixed flocks are often termed ''nuclear species,'' and associating species are termed ''satellite species'' (Moynihan 1962). Nuclear species have conspicuous calls, movement, and coloration, and effective antipredator detection (Amaral and Ragusa-Netto 2008). The nuclear species concept is also relevant for primatology, and at Taï Forest, Côte d'Ivoire the vividly colored and very vocal Diana monkey (Cercopithecus diana) has been called a nuclear species for red colobus monkeys (Procolobus badius), Campbell's monkey (C. campbelli), and lesser spot-nosed monkeys (C. petaurista) by Bshary and Noë (1997a).…”

Gouldian finches are followers with black-headed females taking the lead

“…This is interesting as so far the Long-tailed finch was more seen as a superior competitor with respect to nest holes [31]. In contrast, around waterholes Long-tailed finches may act as a nuclear species [46] for Gouldian finches. Why they prefer this species above others is unknown but may be explained with their co-occurrence across the species’ range and their similar ecological requirements, although the Long-tailed finch is much more a generalist than the Gouldian finch [31].…”