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Brown-headed Nuthatch - Sitta pusilla
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Brown-headed Nuthatch - Sitta pusilla

[Image: Brown-headed-Nuthatch-0037-GWL-06950.jpg]

Scientific classification
Kingdom:  Animalia
Phylum:  Chordata
Class:  Aves
Order:  Passeriformes
Family:  Sittidae
Genus:  Sitta
Species:  Sitta pusilla  Latham, 1790
Subspecies
  • S. p. caniceps
  • S. p. pusilla
  • S. p. insularis
The brown-headed nuthatch (Sitta pusilla) is a small songbird found in pine forests throughout the Southeastern United States. The Bahama nuthatch was and still is considered a subspecies (S. p. insularis) by several authorities including the IOC, but the IUCN and BirdLife International have reclassified it as its own separate species. The bird, like other nuthatches, possesses a sharp black nail-like beak, which it uses to pound open seeds. It is a frequent visitor to feeding stations and is highly fond of sunflower seeds and suet cakes.
Bold and inquisitive, this bird is readily approachable by humans. The bird is frequently observed using a small chip of bark held in its beak as a tool to dig for insects.

[Image: 220px-Brown-headed_Nuthatch-rangemap.png]
Range of S. pusilla


Despite the other species' common name, the brown-headed nuthatch is about the same size as the pygmy nuthatch and the two species are the world's smallest nuthatches. In the brown-headed nuthatch, the total length is 9–11 cm (3.5–4.3 in), wingspan is 16–18 cm (6.3–7.1 in) and body mass is 10–12 g (0.35–0.42 oz). This species sports a brown cap with narrow black eyeline and buff white cheeks, chin, and belly. Its wings are bluish-gray in color. A small white spot is found at the nape of the neck. The bird's call is a sharp whee-hyah sounding very similar to a "rubber duck" toy and particularly is loud for a bird its size. They also make softer "pit pit pit" calls while in flight as well as other squeaking noises. If heard or seen well, this species is virtually unmistakable in the wild, since it overlaps only with the very differently marked and larger red-breasted and White-breasted Nuthatches.



Bird feared extinct rediscovered in the Bahamas

August 23, 2018, University of East Anglia

[Image: birdfearedex.jpg]
One of the rarest birds in the western hemisphere, the Bahama Nuthatch, has been rediscovered by research teams searching the island of Grand Bahama. The finding is particularly significant because the species had been feared extinct following the catastrophic damage caused by Hurricane Matthew in 2016, and had not been found in subsequent searches. But it is feared that there could only be two left -- placing the species on the verge of extinction and certainly among the world's most critically endangered birds. Credit: Matthew Gardner, University of East Anglia

One of the rarest birds in the western hemisphere, the Bahama Nuthatch, has been rediscovered by research teams searching the island of Grand Bahama.

The finding is particularly significant because the species had been feared extinct following the catastrophic damage caused by Hurricane Matthew in 2016, and had not been found in subsequent searches.

But it is feared that there could only be two left—placing the species on the verge of extinction and certainly among the world's most critically endangered birds.

The Bahama Nuthatch is an endangered species, only known from a small area of native pine forest on Grand Bahama Island, which lies approximately 100 miles off Palm Beach, Florida.

University of East Anglia masters students Matthew Gardner and David Pereira set out on a three-month expedition to find this and other endemic Caribbean pine forest bird species.

They made their way through dense forest with thick 'poisonwood' understorey—the layer of vegetation growing beneath the main forest canopy—in what is thought to be one of the most exhaustive searches of the island.

They worked in partnership with Nigel Collar and David Wege from Birdlife International and the Bahamas National Trust, the organisation which works to protect the habitats and species of The Bahama Islands.





Meanwhile a second team of Bahamian students, led by Zeko McKenzie of the University of The Bahamas-North and supported by the American Bird Conservancy, also searched for the bird.

The Bahama Nuthatch has a long bill, a distinctive high-pitched squeaky call, and nests only in mature pine trees. There had been a sharp decline in its population crashing from an estimated 1,800 in 2004 to just 23 being seen in a survey in 2007. The decline likely began in the 1950s due to habitat loss due to timber removal, and more recently due to hurricane damage, storm surges having killed large areas native forest.

Both teams made Nuthatch sightings in May, and the UEA team were lucky enough to capture the elusive bird on film.

Dr. Diana Bell, from UEA's School of Biological Sciences, said: "The Bahama Nuthatch is a critically endangered species, threatened by habitat destruction and degradation, invasive species, tourist developments, fires and hurricane damage.

"Our researchers looked for the bird across 464 survey points in 34,000 hectares of pine forest. It must have been like looking for a needle in a hay stack. They played out a recording of the bird's distinctive call in order to attract it.

"As well as searching for the elusive bird, they also collected environmental data to better understand its habitat preferences and surveyed the extent of hurricane and fire damage," she added."

Matthew Gardner said: "We were the first to undertake such an exhaustive search through 700km of forest on foot.

[Image: 1-birdfearedex.jpg]

"We had been scouring the forest for about six weeks, and had almost lost hope. At that point we'd walked about 400km. Then, I suddenly heard its distinctive call and saw the unmistakable shape of a Nuthatch descending towards me. I shouted with joy, I was ecstatic!"

The UEA team made six Nuthatch sightings in total, and McKenzie's team independently made five sightings, using different methods, in the same small area of forest—including a sighting of what they believe to be two birds together.

Mr Gardner said: "During three months of intensive searching we made six Bahama Nuthatch sightings. Our search was extremely thorough but we never saw two birds together, so we had thought there might only be one left in existence."

"The other team have reported seeing two together so that is promising. However, these findings place the species on the verge of extinction and certainly amongst the world's most critically endangered birds."

"We also don't know the sex of the birds. In many cases when birds dwindle to such small numbers, any remaining birds are usually male."

"The photographs clearly show this distinctive species and cannot be anything else" said Michael Parr, President of American Bird Conservancy and a UEA alumnus.

"Fortunately this is not a hard bird to identify, but it was certainly a hard bird to find," he added.

The Nuthatch was spotted in a small area known as Lucaya Estates. During the research project, birds were seen and heard in three distinct but nearby locations within this area.

[Image: 2-birdfearedex.jpg]

Researcher Zeko McKenzie said: "Although the Bahama Nuthatch has declined precipitously, we are encouraged by the engagement of conservation scientists who are now looking for ways to save and recover the species."

The UEA team however are less optimistic as the exact drivers of the precipitous decline of the bird are still unclear.

Dr. Diana Bell said: "Sadly, we think that the chances of bringing this bird back from the brink of extinction are very slim—due to the very low numbers left, and because we are not sure of the precise drivers for its decline.

"But it is still absolutely crucial that conservation efforts in the native Caribbean pine forest do not lapse as it is such an important habitat for other endemic birds including the Bahama Swallow, Bahama Warbler and Bahama Yellowthroat.

"The habitat is also incredibly important for North American migrants including the Kirtlands Warbler," she added.

Ellsworth Weir, Grand Bahama Parks Manager at the Bahamas National Trust, said: "It has been a pleasure for The Bahamas National Trust to host both Matthew and David as they conducted this very important research on Grand Bahama."

"Their work has taken them across the length and breadth of the island in what was likely the most in depth search to be conducted. Their research, which was inclusive of bird and habitat surveys, has helped to answer questions that some residents have been asking for some time."

"Sadly, we realize now that we are faced with a very dire situation regarding the Bahama Nuthatch. We wouldn't have realized the extent of the issue without the persistent efforts of David and Matthew."

https://phys.org/news/2018-08-bird-extin...hamas.html
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Why fly the coop? With shortage of mates, some birds choose to help others raise offspring

March 14, 2019, Florida State University

[Image: whyflythecoo.jpg]
Doctoral student Jessica Cusick worked with Associate Professor Emily DuVal and Jim Cox, a vertebrate ecologist, on the study about how some birds choose to help others raise their brood. Credit: Tara Tanaka

It's not uncommon for young adults to pitch in and help out with the care of younger siblings. But it turns out that sometimes birds choose to become avian au pairs rather than raise their own brood.

After a five-year experiment, researchers from Florida State University and the Tallahassee-based Tall Timbers Research Station found that when fewer mates were available for brown-headed nuthatches, these small pine-forest birds opted to stay home and help their parents or other adults raise their offspring.

The study is published in the journal Behavioral Ecology.

Associate Professor of Biological Science Emily DuVal and Jim Cox, a vertebrate ecologist from Tall Timbers and a courtesy faculty member at FSU, had long been interested in how these tiny birds showed cooperation—that is often having non-breeding young adults hang out and help raise chicks. After all, bypassing the chance to reproduce is not typically how nature works.

Researchers have often thought that a shortage of males might be one reason for this behavior. To test this idea, they manipulated the ratio of adult males and females throughout Tall Timbers to see exactly how that might affect breeding and cooperation.

Aided by graduate student Jessica Cusick, Cox and DuVal swapped the chicks among 72 nests to create two areas that had an overabundance of either male or all female nuthatches. They also left some areas in between untouched. After two years of observation, they had a year with no manipulation and then reversed the treatments for each area and drove the ratio of males and females in the opposite direction.

"We're trying to understand cooperation from perspective of mate limitations," DuVal said. "Cooperative breeding is a complex social interaction. The idea that you could change such a complex social behavior with a relatively simple manipulation was something we wanted to explore."

The team found that in these areas where the potential mating population was skewed by the manipulation, more of these birds opted to become helpers rather than live on their own or disperse to the buffer zone where there may be more potential mates.

The helper bird engages in activities such as feeding the young or helping feed the mother while she is nesting. The helper might also help defend the nest.

Typically, male birds are more likely to function as a helper in raising chicks, but in the population affected by the manipulation, researchers found an uptick in cooperation by both sexes.

"We saw a slight increase in female helpers," said Cox, who is the study's first author. "It didn't look like a good year for finding mates when young females emerged from their nests and encountered lots of other females nearby. Instead, they stayed and helped out the birds who did mate."

This was the first large-scale, experimental evidence that the sex ratio of males and females could affect cooperative breeding, the researchers said.

Not all birds breed cooperatively, but it is commonly found among crows and jays. Birds with such complex social behavior are often long-lived, and this work built on nearly a decade of careful population monitoring by Cox and his Tall Timbers Research Station team to identify nests and breeding pairs.

The researchers also found that many of the nests took on additional helpers. While there is usually only one bird acting as a helper each year, in this case, some nests had three.

https://phys.org/news/2019-03-coop-short...pring.html



Journal Reference:
James A Cox et al, Manipulated sex ratios alter group structure and cooperation in the brown-headed nuthatch, Behavioral Ecology (2019). DOI: 10.1093/beheco/arz030

Abstract
A biased adult sex ratio (ASR) can influence cooperative breeding behavior if the bias limits mating opportunities for the more abundant sex. We tested predictions associated with the ASR-cooperation hypothesis in the brown-headed nuthatch (Sitta pusilla). We manipulated ASR by cross-fostering known-sex nestlings within 2 large (≥100 ha) experimental plots for 5 years using a crossover design where each plot received an opposing male- or female-biased treatment for 2 consecutive years. A year with no manipulations followed before the bias was reversed on each plot for 2 additional years. Variation in ASR (adult males/total adults) was pronounced compared to background proportions (0.55) and ranged from a female bias in female-biased plots (0.47) to a strong male bias in male-biased plots (0.71). Sex ratios during the postbreeding period ranged more broadly (0.33 in female-biased plots vs. 0.74 in male-biased plots). Territory densities did not change significantly and allowed 6 predictions to be assessed. Consistent with predictions, the prevalence of cooperative breeding groups doubled under male-biased treatments and large cooperative groups appeared (≥2 male helpers vs. the single male helper most common prior to the experiment). These changes occurred despite increased dispersal of cross-fostered males in male-biased plots. Most juvenile females dispersed, but, consistent with predictions, the prevalence of female helpers increased under female-biased treatments. Manipulations did not alter the sex of nestlings produced nor extend the time that males served as helpers. Taken collectively, results support the ASR-cooperation hypothesis and the role that mate limitations play in cooperative breeding behavior.

https://academic.oup.com/beheco/advance-...m=fulltext
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