Tree Swallow - Tachycineta bicolor

[OldGreenVulture]

Tree Swallow - Tachycineta bicolor



Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Hirundinidae
Genus: Tachycineta
Species: Tachycineta bicolor

The tree swallow (Tachycineta bicolor) is a migratory passerine bird that breeds in North America and winters in Mexico, Central America and the Caribbean. It is a very rare vagrant to western Europe.



Range of T. bicolor
Breeding summer visitor
Migration visitor
Winter visitor

Description
This swallow averages 13.5 cm (5.3 in) long and weighs about 20 g (0.71 oz). The bill is tiny. The adult tree swallow has iridescent blue-green upperparts, white underparts, and a very slightly forked tail. The female usually has duller colours than the male, often more greenish than the more bluish male. The juvenile plumage is dull grey-brown above and may have hint of a grey breast band.

Behaviour
Being highly social outside of the breeding season, tree swallows may form flocks of several thousand birds near roost sites. Flocks near Vacherie, Louisiana, were estimated to contain well over 1 million birds during December 2009.





Breeding
Tree swallows nest in natural or artificial cavities near water and are often found in large flocks. They readily use nest boxes, including those built for bluebirds. Declines in cavity-builder populations are resulting in fewer natural nesting sites for tree swallows, although the swallow population remains healthy.

The tree swallow nest consists of multiple layers of grasses and thin twigs, and is often lined with feathers from other species. The female lays four to seven white eggs and incubates them by herself. The eggs hatch in about 14 days and the hatchlings are altricial. The hatchlings typically fledge in 16–24 days. While there are young or eggs in the nest, adults frequently dive bomb intruders (including curious humans) and attempt to drive them from the area. Tree swallows are known to "fight" over feathers in mid-air for reasons which are still under investigation. There is some speculation that this is a form of play.

Tree swallows are typically single-brooded, although they may attempt a second nest if the first fails early in the season. There are records of parents raising two successful broods in a season.



Feeding
They subsist primarily on a diet of insects, sometimes supplemented with small quantities of fruit. They are excellent fliers and take off from their perch and acrobatically catch insects in their bills in mid-air.

Etymology
The genus name is from Ancient Greek takhukinetos, "moving quickly", and the specific bicolor is Latin and means "two-coloured".

From Carnivora.

carnivora.net/-t2462.html?

[OldGreenVulture]

Quality, not quantity, of diet is key to health of baby birds

Date: September 21, 2016
Source: Cornell University


Tree swallow.
Credit: Lily Twining

In a new study that upends the way ornithologists think about a young bird's diet -- but won't shock parents used to scanning the nutritional profile of their children's food -- Cornell researchers have found that when it comes to what chicks eat, quality trumps quantity.

In recent decades, many aerial insectivores, such as tree swallows, have undergone steep population declines. Cornell researchers have demonstrated for the first time that the fatty acid composition in the tree swallow diet plays a key role in chick health and survival rates, potentially pointing to new ways to protect fragile bird species.

"This study really reforms the way ecologists see the food of wild animals," said senior author David Winkler, professor of ecology and evolutionary biology in the College of Agriculture and Life Sciences. "From a preoccupation with how much food is available, we need to turn our eyes to what kind of food is available."

For the study, researchers manipulated the ratio of long-chain omega-3 fatty acids [the good fat present in fish oil] to short-chain omega-3 fatty acids [the good fat in flax seeds] as well as the amount of food. Chicks given diets rich in long-chain omega-3 polyunsaturated fatty acids (LCPUFA) grew faster, were in better condition, had more efficient metabolisms and had a stronger immune response compared with chicks on a low LCPUFA diet.

The researchers found that chicks had higher growth rates and better body condition when they were fed a small amount of high-quality food than if they were fed a large amount of low-quality food.

In addition, chicks fed a small amount of high-quality food had similar immune responses and metabolic rates as those fed a large amount of low-quality food.

In the wild, tree swallows and other aerial insectivores typically forage on a mixture of aquatic and terrestrial insects. Aquatic insects are much richer in LCPUFA than insects that live on land.

"We found that aquatic insects are likely a far more important food source than previously thought due to their high-quality fats," said lead author Lily Twining, a doctoral student in the field of ecology and evolutionary biology. "The destruction and degradation of aquatic habitats that produce insects with long-chain omega-3 fatty acids may be having important negative impacts on tree swallows and other declining aerial insectivores.

"This study provides new clues into how nutrition and food webs impact the decline of prominent species, and provides further incentive to protect freshwater habitats not only for aquatic animals like fish, but also for terrestrial animals like the songbirds in our study," she added.

Tree swallow populations have declined 36 percent in the past three decades, a circumstance explained at times by reduced insect populations, ecological fragmentation and the effects of climate change. Other North American aerial insectivores -- like nighthawks and chimney swifts -- have also undergone similar major disruptions in populations.

This study suggests that the mismatch between the fatty acid composition of insects and the nutritional needs of aerial insectivores could be a crucial driver of fitness and reproductive potential for these birds.

Furthermore, the researchers said tree swallows may be timing breeding to coincide with the peak abundance of high-LCPUFA aquatic insects.

Story Source: Cornell University. "Quality, not quantity, of diet is key to health of baby birds." ScienceDaily. www.sciencedaily.com/releases/2016/09/160921151809.htm (accessed September 22, 2016).




Journal Reference:
Cornelia W. Twining, J. Thomas Brenna, Peter Lawrence, J. Ryan Shipley, Troy N. Tollefson, David W. Winkler. Omega-3 long-chain polyunsaturated fatty acids support aerial insectivore performance more than food quantity. Proceedings of the National Academy of Sciences, 2016; 201603998 DOI: 10.1073/pnas.1603998113

Abstract
Once-abundant aerial insectivores, such as the Tree Swallow (Tachycineta bicolor), have declined steadily in the past several decades, making it imperative to understand all aspects of their ecology. Aerial insectivores forage on a mixture of aquatic and terrestrial insects that differ in fatty acid composition, specifically long-chain omega-3 polyunsaturated fatty acid (LCPUFA) content. Aquatic insects contain high levels of both LCPUFA and their precursor omega-3 PUFA, alpha-linolenic acid (ALA), whereas terrestrial insects contain much lower levels of both. We manipulated both the quantity and quality of food for Tree Swallow chicks in a full factorial design. Diets were either high-LCPUFA or low in LCPUFA but high in ALA, allowing us to separate the effects of direct LCPUFA in diet from the ability of Tree Swallows to convert their precursor, ALA, into LCPUFA. We found that fatty acid composition was more important for Tree Swallow chick performance than food quantity. On high-LCPUFA diets, chicks grew faster, were in better condition, and had greater immunocompetence and lower basal metabolic rates compared with chicks on both low LCPUFA diets. Increasing the quantity of high-LCPUFA diets resulted in improvements to all metrics of performance while increasing the quantity of low-LCPUFA diets only resulted in greater immunocompetence and lower metabolic rates. Chicks preferentially retained LCPUFA in brain and muscle when both food quantity and LCPUFA were limited. Our work suggests that fatty acid composition is an important dimension of aerial insectivore nutritional ecology and reinforces the importance of high-quality aquatic habitat for these declining birds.

www.pnas.org/content/early/2016/09/13/1603998113

From Carnivora.

carnivora.net/-t2462.html?

[Eaglehawk]

Young tree swallows carry environmental stress into adulthood

by Cornell University


Credit: CC0 Public Domain

Cornell University researchers have found that colder temperatures during tree swallows' development stage has an effect on swallows later in life.
For the past seven years, Maren Vitousek, assistant professor of ecology and evolutionary biology, and her research group have been studying a population of tree swallows in the Ithaca area.
When they analyzed breeding and hormone data, the team found a negative relationship between the temperature during the birds' development and their hormonal response to stressors as adults.
"This study is part of a growing body of research showing that relatively minor differences in the environment in which an individual develops can have significant consequences for how they cope with stress later in life," Vitousek said. "This phenomenon could help explain how changing environments are impacting many different species."
Doctoral student Jennifer Uehling, a member of the Vitousek Lab, is lead author of "Developmental Temperature Predicts the Adult Response to Stressors in a Free-living Passerine," which published Dec. 3 in the Journal of Animal Ecology.
"For this study, we followed tree swallows from eggs to adulthood, which is an approach that is rarely possible because it is difficult to follow wild animals over the course of their lives," Uehling said. "If the ambient temperature was cold during natal development, then the adult swallow tended to show a greater increase in glucocorticoid levels in response to a challenge when it was incubating its own young."
Glucocorticoid hormones help regulate metabolism and play a key role in coordinating how birds respond to stressors. In some species, including tree swallows, the levels of these hormones can predict reproductive success in certain contexts.
The data for this study also draw upon on a robust, 30-year dataset of the Ithaca-area tree swallow population. This allowed the team to correlate temperatures during development with the adults' responses to stressors over a greater period of time and understand how the birds were responding to changes in the environment.
"Our study hints that climate change could affect avian survival, reproductive success and populations in a more indirect way," Uehling said. "Changing environmental temperatures during development could affect glucocorticoid levels in adulthood, which mediate adult reproductive success."
The team is already exploring further study.
"One line of research that we are currently pursuing is trying to understand how temperature alters the physiological systems involved in responding to stressors, and whether the internal microbiome plays a role," Vitousek said. "Another big focus of our research is identifying consequences of showing a particular stress coping strategy. How do differences in stress coping strategy influence health and fitness?"

phys.org/news/2019-12-young-tree-swallows-environmental-stress.html

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Journal Reference:
Jennifer J. Uehling et al. Developmental temperature predicts the adult response to stressors in a free‐living passerine, Journal of Animal Ecology (2019). DOI: 10.1111/1365-2656.13137

Abstract

1. Early‐life conditions can have substantial effects on the ways animals respond to stressors as adults. In particular, thermal conditions during development affect juveniles' responses to stressors, and there is evidence that these effects may extend into adulthood. However, these effects remain poorly understood, especially in free‐living organisms.
2. We test the prediction that ambient temperatures during laying, embryonic development and nestling development affect the hormonal mediators of the response to stressors in adults. To do so, we use a long‐term dataset of tree swallows (Tachycineta bicolor) with records from both natal development and adult breeding.
3. We found a strong, negative relationship between ambient temperature during early development (incubation) and an individual's corticosterone (CORT) response to stress later in life (while incubating her own young). Thermal conditions during other stages of natal development also showed a weak relationship with baseline CORT during provisioning.
4. In a post hoc analysis, we found no evidence that ambient temperature during development differentially influenced the survival and recruitment of juveniles with different CORT phenotypes.
5. Our results show that thermal conditions during development can have long‐term effects on how individuals respond to stressors.

besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13137