Tree Swallows Tachycineta Bicolor Research Articles

Decoupling pioneering traits from latitudinal patterns in a north American bird experiencing a southward range shift.

Ecogeographic rules describe spatial patterns in biological trait variation and shed light on the drivers of such variation. In animals, a consensus is emerging that 'pioneering' traits may facilitate range shifts via a set of bold, aggressive and stress-resilient traits. Many of these same traits are associated with more northern latitudes, and most range shifts in the northern hemisphere indicate northward movement. As a consequence, it is unclear whether pioneering traits are simply corollaries of existing latitudinal variation, or whether they override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation. The tree swallow Tachycineta bicolor is a songbird undergoing a southward range shift in the eastern United States, in direct opposition of the poleward movement seen in most other native species' range shifts. Because this organic range shift countervails the typical direction of movement, this case study provides for unique ecological insights on organisms and their ability to thrive in our changing world. We sampled female birds across seven populations, quantifying behavioural, physiological and morphological traits. We also used GIS and field data to quantify a core set of ecological factors with strong ties to these traits as well as female performance. Females at more southern expansion sites displayed higher maternal aggression, higher baseline corticosterone and more pronounced elevation of corticosterone following a standardized stressor, contrary to otherwise largely conserved latitudinal patterning in these traits. Microhabitat variation explained some quantitative phenotypic variation, but the expansion and historic ranges did not differ in openness, distance to water or breeding density. This countervailing range shift therefore suggests that pioneering traits are not simply corollaries of existing latitudinal variation, but rather, they may override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation.

Natural and experimental cold exposure in adulthood increase the sensitivity to future stressors in a free‐living songbird

Abstract As the global climate shifts, many species are imperilled by changing thermal regimes. Despite rising global temperatures, some populations must contend with more frequent or extreme cold. In these populations, the ability to cope with cold may be an important determinant of fitness. Experiments in captive animals have shown that extreme cold or rapid temperature declines typically elicit an increase in glucocorticoid hormones (mediators of the stress response); however, it is not known whether free‐living adults, which may be better at buffering the effects of cold, show a similar response to ecologically relevant thermal challenges. The effects of cold on the sensitivity to future challenges are also poorly understood. Using targeted manipulations of nest temperature in free‐living tree swallows Tachycineta bicolor and a long‐term dataset (2,888 samples; 8 years), we tested the relationship between cold exposure and glucocorticoid levels in adults. Both natural and experimental cold exposure altered glucocorticoid regulation. This manifested primarily in terms of an upregulation in the sensitivity to future challenges (stress‐induced levels). Experimental cold exposure also increased the initial speed and duration of the acute stress response. Analyses of the long‐term dataset found that baseline glucocorticoids were higher in cold conditions; however, the magnitude of this effect was weak. A sliding window analysis revealed differences in the timeline over which temperature best predicted baseline and stress‐induced glucocorticoids. Although unpredictability is often regarded as a defining factor of stressors, we found that recent ambient temperatures better predicted circulating corticosterone than measures of thermal unpredictability, including the degree of recent temperature change and negative prediction error (the difference between experienced temperatures and long‐term averages). Together, these results suggest that thermally induced increases in the sensitivity to future challenges may prime individuals to respond more strongly or rapidly to worsening conditions, or to subsequent challenges of a different type, without incurring the costs that can result from substantial elevations in baseline glucocorticoids. This kind of preparatory response could be adaptive; however, an increased sensitivity to other challenges could also represent an overlooked cost of changing thermal regimes. Read the free Plain Language Summary for this article on the Journal blog.

Determinants of nest box local recruitment and natal dispersal in a declining bird population

Recruitment and dispersal are important demographic rates and studying their determinants is particularly important in the current context of global anthropogenic perturbations. In birds, and especially for migratory species, assessing these rates is challenging because of the difficulties involved in tracking individuals beyond fledging. Here we assessed the determinants of nest box local recruitment and natal dispersal distances in a declining aerial insectivore, the tree swallowTachycineta bicolor. We used a 16‐year dataset obtained from the long term monitoring of a population breeding within a 10 200‐km2study system located along a gradient of agricultural intensification in southern Québec, Canada. Yearly nest box local recruitment rates ranged there in between 1.0% and 3.2%. Heavier nestlings who fledged earlier were more likely to recruit. Natal dispersal distances were generally short (mean ± SD = 12.7 ± 13.8 km) in the study system and were influenced by different factors depending on sex. Females dispersed over shorter distances when conspecific occupancy on breeding site was high, while males dispersed farther in the presence of competing house sparrowsPasser domesticusand when their mother was young. Selection of breeding locations appeared to take place at multiple scales and individuals recruited in sites with characteristics similar to their natal sites. Our results provide important information concerning the factors influencing nest box local recruitment and natal dispersal dynamics of this migratory species. These factors should be considered in conservation practices for this species in order to support production of recruits in habitats favorable to their survival.

Nest decoration: birds exploit a fear of feathers to guard their nest from usurpation.

Many species of birds incorporate feathers into their nest as structural support and to insulate the eggs or offspring. Here, we investigated the novel idea that birds reduce the risk of nest usurpation by decorating it with feathers to trigger a fear response in their rivals. We let prospecting birds choose between a dyad of nest-boxes in the wild, both containing some nest materials, but where one had a few white feathers and the other had none. All three species of cavity-nesting birds studied, the pied flycatcher Ficedula hypoleuca, the blue tit Cyanistes caeruleus, and the tree swallow Tachycineta bicolor, hesitated to enter boxes with white feathers. A similar avoidance of white feathers was found when the alternative nest-box of a dyad held black feathers. However, the birds readily collected white feathers that we placed in front of their nest-box, showing the fear of such feathers was context-dependent. We suggest that naive prospecting birds may perceive feathers in nests as the result of a predation event, and that owners decorate nests with bright feathers that can be seen from the opening to deter others from entering.

A putative telomerase activator has tissue‐specific effects on telomere length in a developing songbird

There is good evidence that telomeres predict variation in health and longevity, yet it is unclear whether these patterns are causally derived from telomeres per se, in part because relatively little research directly manipulates telomere length during early life, when telomere shortening is most dynamic. Here, we test how the telomerase activator TA‐65 (i.e. cycloastrogenol) affects telomere length in five tissues during the peak of growth in the wild tree swallow Tachycineta bicolor. Following eight days of oral TA‐65 administration, chicks experienced telomere lengthening in the blood and accelerated feather growth, but no changes to mass over time. TA‐65 did not affect telomere length in the brain or spleen and led to shorter telomeres in the liver and adrenals. This whole‐organism experimental manipulation of telomere dynamics therefore reveals limitations to telomere protection and biological senescence. In doing so, this work advances our understanding of early‐life telomere dynamics and their potential role in generating future variation in health and lifespan.

Temperature and land use influence tree swallow individual health.

Aerial insectivorous bird populations have declined precipitously in both North America and Europe. We assessed the effects of insect prey availability, climate and shifts in water quality associated with urbanization on haematocrit, haemoglobin concentration and heterophil-lymphocyte (H/L) ratios among ~13-day-old tree swallow (Tachycineta bicolor) nestlings in the Columbus, Ohio area. Higher mean temperature and increased frequency of extreme heat days during the early breeding period (May-June) were linked to reduced nestling physiological condition as evidenced by lower concentrations of haemoglobin and haematocrit, potentially due to increased heat stress, shifts in insect prey availability or altered parental provisioning efforts. Urbanization and the size and density of emergent aquatic insects were associated with elevated physiological stress, whereas higher mean temperatures and terrestrial insect size were related to lower stress as measured by H/L ratios. Overall, these findings highlight the complex environmental conditions driving nestling health, which may be indicative of post-fledging survival and, consequently, population growth. Our results underscore the need for conservation approaches that adequately address the interrelated effects of changes in climate, land use and food resources on aerial insectivorous birds.

Effects of urbanization and nest-box design on reproduction vary by species in three cavity-nesting passerines in the Okanagan Valley, British Columbia, Canada

Artificial nest boxes provide an important resource for secondary cavity-nesting passerines, whose populations may be limited by the availability of nesting sites. However, previous studies have demonstrated that the design and placement of boxes may affect the reproductive success of the birds that use them. In this study, we asked whether the habitat surrounding a nest box or the type of box influenced reproduction in three cavity-nesting passerines. We studied Western Bluebirds (Sialia mexicana Swainson, 1832), Mountain Bluebirds (Sialia currucoides (Bechstein, 1798)), and Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) breeding in artificial nest boxes at sites across 70 km of the Okanagan Valley of British Columbia, Canada. Sites varied in their degree of urbanization, from relatively undisturbed ranchland, to cultivated vineyards, to frequently disturbed “suburban” habitat, and boxes varied in type of entrance (slot or hole). Western Bluebirds nested earlier in vineyards, and Tree Swallows produced significantly fewer fledglings in suburban habitat. In addition, Tree Swallows nested earlier and produced more fledglings in slot boxes. Our results suggest that conservation actions for cavity-nesting passerines may depend on the target species, which in turn should dictate the appropriate box type and habitat when erecting or replacing nest boxes.

Swallow mums push metabolic limits when they can keep cool

![Figure][1] Male tree swallow ( Tachycineta bicolor ) sitting on a birdhouse. Photo credit: Mykola Swarnyk [CC BY-SA ( )] Parenting is not for the faint hearted. Dedicated tree swallow mums and dads commit themselves to 16 h of exertion

Florida's Strategic Position for Collaborative Automated Telemetry Tracking of Avian Movements Across the Americas

Florida's Strategic Position for Collaborative Automated Telemetry Tracking of Avian Movements Across the Americas

Does blood loss explain higher resting metabolic rates in nestling birds with hematophagous ectoparasites?

Nestlings of many bird species are hosts to hematophagous ectoparasites. Parasitism of nestlings is usually sub‐lethal, but its effects can extend into the fledgling and adult stages. Nestling hosts lose enough blood to become anemic, but the effects of reduced oxygen‐carrying capacity on metabolic rate are poorly understood. This study examined the consequences of parasitism by larval blow flies Protocalliphora sialia for nestling tree swallows Tachycineta bicolor. We found that nestlings with more parasites had higher whole‐animal RMR. We evaluated the role of increased erythropoiesis as a potential mechanism explaining increased RMR by drawing blood from some birds. However, we found no evidence that blood loss, as a proxy for hematophagous parasitism, increased metabolic rate. Future work should examine the metabolic costs of upregulation of immunity and how elevated RMR due to ectoparasites affects nestlings as they develop into independent adults.

The relationship between plumage coloration and aggression in female tree swallows

Intrasexual competition is an important selective force that can favor the evolution of honest signals of fighting ability. Research has focused predominantly on male birds, but many female birds also possess plumage ornaments that could mediate the outcome of competitive interactions. We examined the relationship between blue and white structural coloration and aggression in female tree swallows Tachycineta bicolor. Tree swallows are secondary cavity nesters and females show delayed plumage maturation which may be related to intense competition for nest sites. We compared plumage reflectance of second‐year (SY) and after‐second year (ASY) females, and within‐individual changes in plumage reflectance of ASY females in two successive years. We assessed aggression by placing a caged SY female 2 m from the nest box of an ASY female and quantified the ASY female's response in relation to her own plumage coloration. We found substantial differences in plumage reflectance of SY and ASY females, but found that ASY females became greener with duller white coloration in the second year. This may be due to poor weather that made reproduction particularly costly in the first year of the study and suggests coloration is influenced by condition. We found no relationship between dorsal coloration and aggressiveness. Rather, brighter white females spent more time on their nest box and within 2 m of the intruder than females with dull breasts. Our findings suggest that brighter white ASY females may perceive a SY female as less of a threat or that there may be a trade‐off associated with aggression and parental care that is related to white brightness.

Eastern Bluebird (Sialia sialis) feeds Tree Swallow (Tachycineta bicolor) nestlings: Support for location-based decision rule

Interspecific feeding is an uncommon yet widespread phenomenon where an individual of one species feeds the young of another. There are numerous hypotheses to explain why this behavior might occur, but in most cases the observer can only speculate on the cause because they lack information on the nesting histories of the species involved. We observed a color-banded male Eastern Bluebird (Sialia sialis) feed 10-day-old Tree Swallow (Tachycineta bicolor) nestlings in a paired nest box 29 times during a 3 h nest observation. The male bluebird had previously fledged young from the box where the Tree Swallows were currently nesting and currently was nesting in the paired box, suggesting that the probable cause for this reproductive error was both the close proximity of the box and an attachment to the box where he had previously raised young. This observation suggests that instead of identifying the young by call, the male was using a place-based decision rule when he responded to the calls from the box where he had previously nested. Pairing nest boxes, a common practice used to reduce competition for nest boxes between bluebirds and Tree Swallows, may inadvertently increase the probability of interspecific feeding as a result of location-based decision rules for feeding and care of young.

How robust are risk-taking associations in incubating birds? A test and a review

Flushing distance (FD, the horizontal distance between a parent bird when it leaves its nest and an approaching predator) is one measure of nest defense and of risk-taking; parents that stay too long risk being killed, whereas those that flush too early risk at the very least impairing development of their young, and at the very worst leaving them unprotected against predators. Thus, FD should be under strong natural selection. A general prediction is that incubating birds will remain on a nest being approached by a predator until risks of staying reach a threshold that outweighs costs of fleeing. This threshold is predicted to vary depending on a brood’s value, parental characteristics, environmental conditions, and learning that repeated visits pose a limited or no threat. We evaluated FD in a nest box population of tree swallows (Tachycineta bicolor) relative to each of these. We obtained 246 FDs from 66 different nests over 2 years. We found some evidence that FD increased with clutch size (tendency), female age, and air temperature, and decreased with greater overhead vegetation density; six additional associations were not significant. Given the lackluster support for the predictions we tested, we did a review of the literature and similarly found limited support for most of the associations we tested despite the entrenched view that these relationships are commonplace. We submit that further insights are needed into understanding predictors of FD in incubating birds. SIGNIFICANCE STATEMENT: Parent birds sitting on eggs are proverbial sitting ducks, although they do have the option of fleeing predators. However, parents may be willing to sacrifice themselves to protect their eggs if the latter become sufficiently valuable. One assumption is that eggs increase in value closer to hatch, and one prediction is that parents will be more reluctant to fly from their nests later in incubation. We tested this and other predictions in a population of nest-box-using tree swallows in eastern North America. The relatively weak support we obtained for our predictions suggests that we need to reevaluate our assumptions in this area of research.

Feather mites of the genus Trouessartia Canestrini (Acariformes: Trouessartiidae) from swallows (Passeriformes: Hirundinidae) in Canada.

Seven species of the feather mite genus Trouessartia Canestrini, 1899 (Astigmata: Trouessartiidae) have been recorded on swallows and martins (Passeriformes: Hirundinidae) in Manitoba (Canada). Of them, five are described as new species: Trouessartia ampulicaudata sp. n. and T. petrochelidon sp. n. from the American cliff swallow Petrochelidon pyrrhonota (Vieillot), T. bochkovi sp. n. from the tree swallow Tachycineta bicolor (Vieillot), and T. cryptocaudata sp. n. and T. progne sp. n. from the purple martin Progne subis (Linnaeus). A new species group stelgidopteryx, incorporating Trouessartia species living on hirundinids of the genera Progne, Tachycineta and Stelgidopteryx, is established. Renewed diagnoses of four Trouessartia species groups (appendiculata, crucifera, minutipes, and stelgidopteryx) restricted to hirundinids and a key to species recorded so far and potentially expected on swallows of North America are proposed. Host associations of Trouessartia species with swallows in North America are briefly discussed.

Element Concentrations in Tree Swallows (Tachycineta bicolor) from the U.S. and Binational Great Lakes Areas of Concern.

Selected elements were targeted in state Remedial Action Plans as one group of chemicals affecting the Beneficial Use Impairments of Great Lakes Areas of Concern (AOCs). Livers of nestling tree swallows, Tachycineta bicolor, were harvested from 76 sites in the Great Lakes, which included multiple sites at 27 AOCs and 12 reference sites from 2010 to 2015, and were analyzed for 21 elements. Mercury concentrations were at background levels at all sites. Elevated cadmium (Cd) concentrations were associated with industry. The highest Cd values were from the Black River, OH AOC and were associated with historic coke production but were not at toxic levels. Lead (Pb) concentrations were highest on the Rouge River, MI AOC-the oldest and most heavily populated and industrialized area in southeast Michigan. Individual Pb concentrations were elevated to a level associated with delta-aminolaevulinic acid dehydratase inhibition but not to a level considered toxic. In contrast, livers harvested from sites on the southwest shore of Lake Michigan had selenium (Se) concentrations elevated to levels associated with reduced avian reproduction. One likely source of the high Se concentrations was pollution from a local coal-fired power plant. Concentrations of the remaining elements were at background levels.

Solar-powered radio tags reveal patterns of post-fledging site visitation in adult and juvenile Tree Swallows Tachycineta bicolor.

The availability of small, lightweight tracking devices enhances our ability to study birds during mobile phases of their lives. Tree Swallows Tachycineta bicolor, a model species of wild songbird, are well-studied during their breeding season; but our understanding of their biology at other times of the year, when they are not tied to the fixed location of a nest, is more limited. We developed a lightweight radio tag with no battery (solar nanotag) to study the movements of small animals, and we deployed it to explore the behavior of Tree Swallows after the end of their summer breeding season. We tagged 32 breeding adult swallows and 36 juveniles and monitored their presence and absence at the breeding site during the post-fledging period. Although our observations are based on very small sample sizes, the tags revealed previously unknown patterns in Tree Swallow behavior during the post-breeding season. Some Tree Swallow fledglings continued to visit the site repeatedly in the months following the nesting season, with the latest detection occurring on September 30th; by contrast, all adults had permanently departed by the end of July. These results inform future hypotheses about post-breeding movements in Tree Swallows. But, more generally, the detection of tagged swallows on their distant wintering grounds, seven months after tagging, indicates the potential of studying small passerine movements throughout their entire lifetimes, and suggests a rich array of applications for these “Life Tags” to study the movements of small animals world-wide.

Nest feathering responses by Tree Swallows (Tachycineta bicolor) to experimental warming

Among many functions, bird nests protect eggs, developing young, and incubating adults from inclement weather. In Tree Swallows (Tachycineta bicolor), prior to and while females are incubating, males compete with rivals for feathers that they use to line nests. The thermal benefits hypothesis proposes that males add feathers to improve heat retention of nests. We tested this hypothesis on Tree Swallows nesting near Wolfville, Nova Scotia, Canada in 2013, 2014, and 2015, and in St. Denis, Saskatchewan in 2013. In 2013, at both locations we experimentally heated nests. After young had fledged, we counted and measured feathers in each nest. The hypothesis was not supported. The only significant result was that St. Denis (52.2°N) had fewer feathers than the Annapolis Valley (45.1°N) site, which is contrary to expectation. Our findings challenge the prevailing hypothesis for why male Tree Swallows feather nests.

Annual variation in polychlorinated biphenyl (PCB) exposure in tree swallow (Tachycineta bicolor) eggs and nestlings at Great Lakes Restoration Initiative (GLRI) study sites.

Tree swallow (Tachycineta bicolor) eggs and nestlings were collected from 16 sites across the Great Lakes to quantify normal annual variation in total polychlorinated biphenyl (PCB) exposure and to validate the sample size choice in earlier work. A sample size of five eggs or five nestlings per site was adequate to quantify exposure to PCBs in tree swallows given the current exposure levels and variation. There was no difference in PCB exposure in two randomly selected sets of five eggs collected in the same year, but analyzed in different years. Additionally, there was only modest annual variation in exposure, with between 69% (nestlings) and 73% (eggs) of sites having no differences between years. There was a tendency, both statistically and qualitatively, for there to be less exposure in the second year compared to the first year.

Avoidance, tolerance, and resistance to ectoparasites in nestling and adult tree swallows

We examined avoidance, tolerance, and resistance strategies of nestling and adult tree swallows Tachycineta bicolor in response to ectoparasitic blowflies Protocalliphora sialia. Tree swallows avoided settling in north‐facing nest boxes early in the breeding season. These boxes were more likely to be parasitized later in the season, suggesting that box selection may facilitate blowfly avoidance. After experimentally manipulating blowfly intensity, we found that nestlings were generally tolerant of parasitism. Parasites significantly reduced nestling blood hemoglobin but had no effect on nestling body mass, primary feather growth, age at fledging, or fledging success. Parents of parasitized nestlings did not increase their food provisioning rate to promote nestling tolerance. Adult female tree swallows demonstrated both tolerance and resistance: blowfly parasitism had no effect on adult hemoglobin and body mass, and those with higher P. sialia‐binding antibody levels had fewer blowfly larvae in their nests. Nestling antibodies were unrelated to blowfly intensity. Despite considerable variation among years, our results suggest that the costs of blowfly parasitism to nestling and adult tree swallows are modest, and limited to blood loss in nestlings. Future work should examine the effects of reduced blood hemoglobin on fledgling survival and the importance of parasite‐specific antibodies.

Do interspecific image-based ageing guides produce accurate estimates of nestling ages? – progress toward development of a generalised ageing guide

ABSTRACTImage-based ageing guides of passerine nestlings can produce accurate age estimates. If different species develop similarly, but timing of development differs, creation of a generalised image-based ageing guide for use with nestlings of multiple species is justified if age estimates can be corrected to account for such differences of timing. To explore this idea, inexperienced participants used an image-based ageing guide for Tree Swallow Tachycineta bicolor nestlings to produce age estimates from images of known-age nestling Eastern Bluebirds Sialia sialis and House Wrens Troglodytes aedon. Participants also used a House Wren ageing guide to produce age estimates of nestling Eastern Bluebirds and an Eastern Bluebird ageing guide to produce age estimates of House Wren nestlings (n = 54 total participants and 2565 age estimates). Ages of nestling bluebirds were generally underestimated with the swallow and wren ageing guides, while ages of wrens were generally overestimated with the swallow and bluebird guides. Although the accuracy of age estimates (the percentage within one day of actual age) produced by interspecific guides ranged from 43% to 77% overall, accuracy of estimates corrected using regression analyses increased to better than 80% for all pairwise comparisons. Based on these results, continued development and refinement of a generalised nestling ageing guide is warranted.