Tag Archives: hummingbirds

Feeding strategies in competing hummingbird species observed in a small area in Brazil

(Pensoft Publishers; 2 May 2017; Photo: Lucas Lanna)

Being the vertebrates with the highest metabolic rate thanks to their rapid wing flaps, the hummingbirds have evolved various types of feeding behaviour. While the nectar-feeders tend to go for food high in energy, strong competition affects greatly their preferences and behaviour towards either dominance, subordination, a strategy known as trapline and a fourth one named hide-and-wait, conclude the Brazilian scientists Lucas L. Lanna, Cristiano S. de Azevedo, Ricardo M. Claudino, Reisla Oliveira and Yasmine Antonini of Universidade Federal de Ouro Preto. Their conclusions following six months of observations in an Atlantic Forest remnant in southeastern Brazil are published in the open access journal Zoologia.

To test previous assumptions as well as their own hypotheses, the researchers placed artificial bird feeders filled with variable in concentration sugar-water solutions across four separate patches at the core of the forest fragment.

The scientists sought to find out whether the birds would show clear preference for the most sugary food source; whether larger size and heavier weight would guarantee better access to the most nutritious feeders; what strategies would be adopted by each species; and which ones would prove the dominant and most aggressive.

As expected, the scientists concluded that the birds prefer the most sugar-dense solutions. However, when subordinate species, such as the white-throated hummingbird and the versicoloured emerald, confronted dominant species guarding the most nutritious food sources, they would be either frightened or expelled following a short chase. Subsequently, these hummingbirds would resort to the feeders with low-sugar solutions.

In their turn, the Brazilian ruby and the violet-capped woodnymph proved to be the dominant and most aggressive species in the studied area. Upon seeing an ‘intruder’ in their territory, which might be either another species, or belonging to their own, they would vocalise their threats, alert them by perching by the feeder, or expel them following a short pursuit. However, they would only try to limit the access for subordinate hummingbirds if the energy that could be gained from the feeder exceeded the energy loss of the chase.

Contrary to another initial hypothesis, it was not the largest and heaviest species that were the dominant ones. There were two species of hermit hummingbirds which were the largest and the heaviest, however, they expressed no territorial or aggressive behaviour. Instead, they were recorded intruding in the territory of the two dominant hummingbird species. In their turn, the Brazilian ruby and the violet-capped woodnymph would often frighten them. Nevertheless, rather than fleeing, the ‘castaways’ were seen hiding in the shrubs, remaining quiet, and returning to the feeder as soon as the dominant bird was gone. This behaviour strategy, named hide-and-wait, has not been reported in hermit hummingbirds prior to this study, according to the authors.

Having reported all feeding strategies in their study, the scientists conclude that the dominant territorial species and the trapliners feed most frequently and most sufficiently, as they use the most sugary sources.

However, the authors note that the high abundance of food, as well as the presence of aggressive territorial species might have affected the hummingbirds’ behaviour and preferences.

Animal Sex: How Hummingbirds Do It

hummingbirds.jpg( Joseph Castro; 5 Marh 2017)

Endemic to the Americas, hummingbirds are defined by their small stature and dart-like movements. But when it comes to mating, do these aerial experts keep things equally quick or do they instead take the slow and steady approach?

Given hummingbirds’ propensity to congregate around flowers and artificial feeders, one might expect that they’re gregarious creatures, but this is far from the truth. In fact, hummingbirds are generally solitary, territorial birds, and most of the time they can be quite aggressive to one another, regardless of sex. “Hummingbirds are mean to everybody,” said Kristiina Hurme, a behavioral ecologist at the University of Connecticut.

Hummingbirds typically limit their social interactions to feeding and mating. The breeding season varies between species, but it often coincides with the rain, which causes a spike in the abundance of insects, said Alejandro Rico-Guevara, an ecologist and evolutionary biologist with the University of Connecticut and University of California-Berkeley. This rich source of protein is needed for plumage molting and egg production, as well as feeding chicks.

How hummingbirds go about mating also varies. “Every single species has a special ritual or mating display,” Rico-Guevara told Live Science. “And they are super complicated.”

Forest-dwelling hermit hummingbirds (those of the subfamily Phaethornithinae) often adhere to a so-called lek mating system, in which males gather in an open area to try to woo females, which visit the males one-by-one. The males, which maintain small territories, start by chirping. This sound is seemingly simple to human ears, but it actually contains layers of complexity when slowed down with computers. “[Hummingbirds] may not only be able to see in high speed but also listen in high speed,” Rico-Guevara said.

An impressed female will perch near a singing male, prompting him to perform tricks to further entice her. These alluring moves may include making sounds with his bill, flying around the female, flying side-to-side in front of her, and displaying his tail and his feathers.

Fights among competing males aren’t uncommon………

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