Troglodytes Aedon Research Articles

Depressed nestling growth during exposure to smoke from distant wildfires

Human and animal populations increasingly encounter smoke pollution as climate change enhances the frequency and intensity of wildfires. Most work on smoke effects in animals has studied populations close to fires, populations experiencing small, prescribed burns, or animals in the lab. In June of 2023, smoke from distant Canadian wildfires quickly elevated particulate matter (PM2.5) pollution in a wild house wren (Troglodytes aedon) population for three days before returning to baseline levels. Compared to previous years, nestlings experiencing three days of elevated PM2.5 within the first 6 days of life weighed less on days 6 and 10 after hatching and had shorter tarsometatarsus bones, a sign of smaller skeletal size. In contrast, nestlings that hatched before or after this event did not differ in size from previous years. Although sublethal, these effects may have important consequences for survival and reproduction. As wildfire activity increases, more wildlife populations are at risk of smoke-related fitness consequences, even those distant from the blaze.

Risk Assessment During Nest Defense Against Three Simulated Predators by Female Northern House Wrens (Troglodytes aedon).

Offspring predation is one of the greatest obstacles to an organism's reproductive success, but parents vary in the strength of their response to potential predators. One explanation for this variable investment is that defending current offspring has the potential to lower future reproductive success if the predator is also capable of injuring or killing the parent. Northern house wrens (Troglodytes aedon) are cavity-nesting songbirds that defend against multiple species of nest predators including small mammals, birds of prey, and snakes. Here, we used three different predator decoys: two nest predators-an eastern chipmunk (Tamias striatus) and an eastern ratsnake (Pantherophis alleghaniensis)-as well as a predator of both offspring and adults-a juvenile Cooper's hawk (Accipiter cooperi)-to elicit nest defense and test whether females use risk assessment to modulate their antipredator behavior. We found that antipredator behaviors were not significantly different between the two nest predators, which posed a high risk to the nestlings, but lower risk to the parents, as neither species frequently captures adult wrens outside the nest box. However, female wrens never dove at or attacked the Cooper's hawk, while they frequently attacked both the snake and chipmunk decoys. Neighboring house wrens from adjacent territories were also less likely to respond to the hawk, but more heterospecifics mobbed the hawk than the snake decoy. Collectively, these results show that risk assessment and the strength of the antipredator response varies substantially both within and among species. Female house wrens exhibit plasticity in their nest defense behavior, and they respond to different types of predators in a way that could maximize lifetime fitness while risking the loss of their current offspring.

Weak population structure in the North American house wren Troglodytes aedon

Cryptic genetic differentiation is being increasingly documented in birds and other organisms using genome‐wide variation. A recent example of cryptic genetic differentiation in a widespread species with conserved morphology is the northern house wren Troglodytes aedon. We found that, despite extremely similar morphology and no documented vocal differences, the two subspecies of the northern house wren, T. a. aedon (eastern) and T. a. parkmanii (western), exhibited both nuclear and mitochondrial genomic differentiation. Individuals present along the Front Range of the Colorado Rocky Mountains possessed nuclear genetic variation intermediate between T. a. aedon and T. a. parkmanii; additionally, both divergent mitochondrial lineages, corresponding to the western and eastern northern house wren populations, occur in Colorado. However, the dynamics of this putative contact zone (i.e. amount of hybridization or introgression) and the degree of differentiation between the two subspecies remain uncharacterized. To expand our understanding of northern house wren population genetic differentiation and explore the possibility of hybridization, we used a double digest restriction‐site associated (ddRAD) approach and sequenced 127 northern house wrens, including 109 individuals from across Colorado and Wyoming, as well as nine individuals each from eastern and western allopatric regions. Our results highlight that T. a. aedon occur significantly further west than previously thought, and provide evidence for weak population structure within the northern house wren, while generally setting the stage for future investigations of northern house wren population genomics and the genetic basis of cryptic speciation.

Behavioural co‐option of plant secondary compounds by a cavity‐nesting bird is an adaptation against competition and predation

Abstract Interactions with competitors and predators can generate strong selection and favour the evolution of novel strategies for mitigating fitness costs. Adaptations to mitigate competition and predation risk often involve evolution of traits which directly reduce costs. Simultaneously, the evolution of behaviours that co‐opt the functional traits of non‐interacting, third‐party species have also been observed but remain poorly studied (e.g. anointing behaviour, tri‐trophic interactions). Here we investigate if the novel behavioural co‐option of conifer resin in a cavity‐nesting bird can ameliorate interactions with nest predators and nest site competitors. Red‐breasted nuthatches (Sitta canadensis) collect resin from live trees and apply it around the entrances of their nest cavities in dead trees. Using paired nest boxes, we mimicked the nuthatch behaviour by apply resin around the hole of one and not the paired box in two field experiments to test a priori hypotheses about the evolution and adaptive value of this behaviour. The first experiment baited the paired boxes with food to attract mammalian predators (e.g. red squirrels Tamiasciurus hudsonicus). The second experiment left boxes available for breeding by cavity‐nesting birds that compete with nuthatches for nest sites (e.g. house wrens Troglodytes aedon). We also used ancestral trait reconstruction to test whether resin use is a non‐adaptive derivation of mud‐plastering behaviour observed in numerous congeners. Experimental nest boxes with resin applied to the entrance were less likely to have bait removed and less likely to have nests built or initiated than paired nest boxes without resin. Ancestral trait reconstruction suggested that resin use was more likely (>77%) to have evolved in ancestors that did not exhibit mud‐plastering behaviour. Our results do not support a major role of phylogenetic inertia and provide experimental evidence that application of conifer resin to nest cavities ameliorates interference competition from other cavity‐nesting species and reduces nest predation risk. Overall, our results showcase the ecological function of behavioural co‐option and its important consequences for fitness in nature. Read the free Plain Language Summary for this article on the Journal blog.

Repeatability of an extended phenotype: Potential causes and consequences of nest variation in Troglodytes aedon (Northern House Wren)

ABSTRACT Construction behavior is an aspect of the extended phenotype that allows organisms to build structures that alter their environments in potentially beneficial ways. Although individuals vary in the expression of this extended phenotype (e.g., structure morphology), the repeatability of construction behaviors remains understudied, especially among free-living populations. Many oviparous taxa construct nests, making them of particular interest because variation in nest architecture may directly affect fitness. Using a free-living, cavity-nesting songbird, Troglodytes aedon (Northern House Wren), as our model, we estimated the contribution of the primary builder (the female) to nest variability by measuring the repeatability of nest morphology between successive clutches. We further examined whether nest morphology was related to the dimensions of the nesting cavity, breeding date, or nest success. We found the composition of the cup lining to be a highly repeatable feature of the nesting female’s nest, although the size and composition of the structural platform appeared more related to the dimensions of the cavity. Nest morphology remained variable throughout the breeding season, showing no significant correlations with breeding date, and it was unrelated to clutch size or offspring survival. Our study suggests that variation in construction behavior is likely the product of multiple factors including the preferences of the builder and physical constraints. The absence of any clear links between construction behavior and fitness indicates that nest morphology is not under strong selection. As a result, diverse female building preferences may explain the extreme among-individual variation in nest structure in this species.

SONG FREQUENCY SHIFTS IN AN URBAN BIRD SPECIES OPTIMIZE ACOUSTIC TRANSMISSION INSIDE NOISY URBAN AREAS

In animal acoustic communication is necessary that signals arrive to the receiver with reduced degradation and attenuation for a better transmission of the message. The noise pollution resulting from anthropogenic activities in cities reduces efficiency and efficacy of acoustic communication. Some species respond to high levels of noise increasing the minimum frequency of their vocalizations to avoid noise masking, but this may affect how sounds transmit in the environment because sounds with higher frequencies experience greater levels of attenuation and degradation. Using a transmission experiment, we analyzed how minimum frequency shifts, affect the sound transmission properties of the song of the House Wren (Troglodytes aedon) in urban areas that differ in the level of anthropogenic noise. We broadcasted songs with minimum frequencies between 1.2-1.8 kHz and the same songs with a minimum frequencies increment artificially of one semitone, increasing minimum frequencies to 2.1-2.6 kHz, in high and low noise level territories at four distances. We quantified signal-to-noise ratio, tail-to-signal ratio, blur ratio, and excess attenuation. Our results showed that songs with frequencies low minimum frequencies in low noise territories transmit with higher signal-to-noise ratio, and lower blur ratio and excess attenuation at longer distances. Songs with increased minimum frequencies only showed higher signal-to-noise ratio in noisier territories at longer distances. These results support the hypothesis of producing frequency shift to increase the communication distance in noisier environments. This is the first experimental study that tests the effect of shifting frequency on acoustic communication transmission on bird territories with different noise levels.

Behavior and survival of parasitic Shiny Cowbird (Molothrus bonariensis) fledglings

Abstract For songbirds, the post-fledging period is critical for development and survival, as young must learn to get food, practice flying, and identify predators to become independent from their parents and disperse or migrate. Obligate avian brood parasites, like cuckoos and cowbirds, lay eggs in nests of other bird species that provide parental care until the parasite’s young become independent. The information on the post-fledging period in songbirds is limited due to the difficulty in following and observing fledglings and it is even scarcer for brood parasites. We studied the behavior, survival, and age of independence of Shiny Cowbird (Molothrus bonariensis) fledglings raised by two hosts that differ markedly in body size: the House Wren (Troglodytes aedon) and the Chalk-Browed Mockingbird (Mimus saturninus). We radio-tracked individuals from a few days before they left the nest until they disappeared from the natal territory. We found: 1) chicks left the nest when they were 11-15 days of age and the age of fledgling did not differ between the two host species, 2); after leaving the nest, they spent most of the time perched in a hidden place without begging but as they grew, the proportion of time perched without begging decreased and begging in hidden and exposed places increased, 3) we observed approaches between adult parasitic females and young in host territories, 4) young abandoned the host territory and joined conspecific flocks when they were 35-39 days of age, and 5) the estimated post-fledging survival was between 12.5% and 20.8%.

Egg Mercury Concentration and Egg Size Varies with Position in the Laying Sequence in two Songbird Species.

In birds, mercury embryotoxicity can occur through the transfer of mercury from the female to her eggs. Maternal transfer of mercury can vary by egg position in the laying sequence, with first-laid eggs often exhibiting greater mercury concentrations than subsequently laid eggs. We studied egg mercury concentration, mercury burden (total amount of mercury in the egg), and egg morphometrics by egg position in the laying sequence for two songbirds: tree swallows (Tachycineta bicolor) and house wrens (Troglodytes aedon). Egg mercury concentration in the second egg laid was 14% lower for tree swallows and 6% lower for house wrens in comparison with the first egg laid. These results indicate that in both species, after an initial relatively high transfer of mercury into the first egg laid, a smaller amount of mercury was transferred to the second egg laid. This lower mercury concentration persisted among all subsequently laid eggs (eggs three to eight) in tree swallows (all were 14%-16% lower than egg 1), but mercury concentrations in subsequently laid house wren eggs (eggs three to seven) returned to levels observed in the first egg laid (all were 1% lower to 3% greater than egg 1). Egg size increased with position in the laying sequence in both species; the predicted volume of egg 7 was 5% and 6% greater than that of egg 1 in tree swallows and house wrens, respectively. This change was caused by a significant increase in egg width, but not egg length, with position in the laying sequence. The percentage of decline in mercury concentration with position in the laying sequence was considerably lower in tree swallows and house wrens compared with other bird taxonomic groups, suggesting that there are key differences in the maternal transfer of mercury into songbird eggs compared with other birds. Finally, we performed simulations to evaluate how within-clutch variation in egg mercury concentrations affected estimates of mean mercury concentrations in each clutch and the overall sampled population, which has direct implications for sampling designs. Environ Toxicol Chem 2024;43:1844-1854. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Birds in urban environments: parks as wildlife refuges in Western Panama

Urban parks play a fundamental role in preserving relict biodiversity in urbanized environments.A study was carried out on the birdlife present in 5 urban Parks in the Western Region of Panama (David): Altos del Morazán, Ivu Primavera, 28 de Noviembre, Plaza Bolívar, Paco García.A total of450 individuals distributed in 8 orders, 18 families and 33 species were reported.The most abundant species were: the Orange-chinned Parakeet (Brotogeris jugularis), the Ruddy ground dove (Columbina talpacoli), the Blue-gray Tanager (Thraupis episcopus), the House Wren (Troglodytes aedon) and the Great-tailed grackle (Quiscalus mexicanus).Three migratory species were recorded:Empidonaxsp.,Piranga rubraandSetophaga petechia. The information presented is baseline and contributes to knowledge about biodiversity in urban environments in Western Panama

On the use of anthropogenic materials in nest building of House Wren (Troglodytes aedon), a report from Parque Los Algarrobos, Cumbayá, Ecuador

Urbanization has prompted shifts in avian nesting behaviors, with some bird species incorporating anthropogenic nest materials (ANMs) into their nests. This study focuses on Troglodytes aedon (House Wren) in Ecuador, exploring the factors influencing their use of ANMs. Observations in Parque Los Algarrobos revealed a House Wren carrying a piece of transparent plastic, entering a street lamp and emergind from it without the plastic. Additional data from iNaturalist showcased widespread ANM use in House Wren nests across Ecuador.

Differences in vocal brain areas and astrocytes between the house wren and the rufous-tailed hummingbird.

The house wren shows complex song, and the rufous-tailed hummingbird has a simple song. The location of vocal brain areas supports the song's complexity; however, these still need to be studied. The astrocytic population in songbirds appears to be associated with change in vocal control nuclei; however, astrocytic distribution and morphology have not been described in these species. Consequently, we compared the distribution and volume of the vocal brain areas: HVC, RA, Area X, and LMAN, cell density, and the morphology of astrocytes in the house wren and the rufous-tailed hummingbird. Individuals of the two species were collected, and their brains were analyzed using serial Nissl- NeuN- and MAP2-stained tissue scanner imaging, followed by 3D reconstructions of the vocal areas; and GFAP and S100β astrocytes were analyzed in both species. We found that vocal areas were located close to the cerebral midline in the house wren and a more lateralized position in the rufous-tailed hummingbird. The LMAN occupied a larger volume in the rufous-tailed hummingbird, while the RA and HVC were larger in the house wren. While Area X showed higher cell density in the house wren than the rufous-tailed hummingbird, the LMAN showed a higher density in the rufous-tailed hummingbird. In the house wren, GFAP astrocytes in the same bregma where the vocal areas were located were observed at the laminar edge of the pallium (LEP) and in the vascular region, as well as in vocal motor relay regions in the pallidum and mesencephalon. In contrast, GFAP astrocytes were found in LEP, but not in the pallidum and mesencephalon in hummingbirds. Finally, when comparing GFAP astrocytes in the LEP region of both species, house wren astrocytes exhibited significantly more complex morphology than those of the rufous-tailed hummingbird. These findings suggest a difference in the location and cellular density of vocal circuits, as well as morphology of GFAP astrocytes between the house wren and the rufous-tailed hummingbird.

Male song structure predicts offspring recruitment to the breeding population in a migratory bird.

Bird song is a classic example of a sexually selected trait, but much of the work relating individual song components to fitness has not accounted for song typically being composed of multiple, often-correlated components, necessitating a multivariate approach. We explored the role of sexual selection in shaping the complex male song of house wrens (Troglodytes aedon) by simultaneously relating its multiple components to fitness using multivariate selection analysis, which is widely used in insect and anuran studies but not in birds. The analysis revealed significant variation in the form and strength of selection acting on song across different selection episodes, from nest-site defense to recruitment of offspring to the breeding population. Males that sang more song typically employed in close communication sired more offspring that were subsequently recruited to the breeding population than those that sang more far-communication song. However, this relationship was not consistent across earlier selection episodes, as evidenced by non-linear selection acting on these song components in other contexts. Collectively, our results present a complex picture of multivariate selection on male song structure that would not be evident using univariate approaches and suggest possible trade-offs within and among song components at different points of the breeding season.

Annual variation of adult survival of a south-temperate House Wren population in Argentina

Annual variation of adult survival of a south-temperate House Wren population in Argentina

Seasonal changes in diet, immune function, and oxidative stress in three passerines inhabiting a Mediterranean climate.

Oxidative status and immune function are energy-demanding traits closely linked to diet composition, particularly resource availability and nutritional value. In seasonal environments, nutrient availability and diet quality fluctuate, potentially influencing these traits. However, limited evidence exists regarding these dietary effects on immune function in seasonal environments. In this study, we employed stable isotope analysis to assess the impact of seasonal changes in niche width and trophic level (i.e., δ15N) on two immune variables (hemolysis and hemagglutination scores) and two oxidative status parameters (lipid peroxidation and total antioxidant capacity) in three passerine species: Zonotrichia capensis (omnivorous), Troglodytes aedon (insectivorous), and Spinus barbatus (granivorous). We found that hemolysis scores varied seasonally in Z. capensis, with higher values in winter compared to summer. Total antioxidant capacity (TAC) also increased during the winter in Z. capensis and S. barbatus. The isotopic niche width for Z. capensis and S. barbatus was smaller in winter than in summer, with the omnivorous species exhibiting a decrease in δ15N. Despite the seasonal shifts in ecological and physiological traits in Z. capensis, we identified no correlation between immune response and TAC with trophic level. In contrast, in the granivorous S. barbatus, the lower trophic level resulted in an increase in TAC without affecting immunity. Our findings revealed that dietary shifts do not uniformly impact oxidative status and immune function across bird species, highlighting species-specific responses to seasonal changes. This underscores the importance of integrating ecological and evolutionary perspectives when examining how diet shapes avian immunity and oxidative balance.

Latitudinal and elevational variation in the reproductive biology of house wrens, Troglodytes aedon.

While cross-species comparisons of birds suggest that as latitude decreases or elevation increases, clutch size decreases and the duration of developmental stages and parental attentiveness increases, studies comparing populations of the same species are rare. We studied populations of house wrens, Troglodytes aedon, at high and low elevations in California and Costa Rica, collecting data on clutch size, the duration of incubation and nestling periods, parental attentiveness, nestling growth rate, and nesting success. Our data support results from cross-species comparisons, but also revealed unanticipated results from low elevation temperate zone house wrens in the southwest. This population had prolonged incubation and nestling periods similar to those found in the tropics. We also found that temperate zone females, especially those at our higher elevation site, spent more of their day incubating than did tropical females. Nest temperature at our high elevation temperate zone site was higher than that at all other tropical sites. Age at fledging did not differ between sites. Total feeding rates per chick and male feedings per chick did not vary between sites. Nest success rates showed the predicted effect of latitude, but not the predicted effects of elevation. Our results extend low elevation house wren research into the southwestern US and contribute the first intraspecific elevational comparison in the Neotropics. Data from our low elevation southwestern site present a unique suite of life history traits that align more with tropical house wrens, although with a larger clutch size, and point to food limitation and/or high predation pressure as being possible drivers of some of these differences. These results highlight the need for additional studies of house wrens and other broadly distributed species at a more diverse array of sites to better understand which forces drive the evolution of different life history strategies across major biogeographical gradients.

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Decision rules for egg-color-based rejection by two cavity-nesting hosts of the brown-headed cowbird.

Hosts of obligate avian brood parasites often evolve defense mechanisms to avoid rearing unrelated young. One common defense is egg rejection, for which hosts often rely on eggshell color. Most research has assumed that hosts respond to perceived color differences between their own eggs and parasite eggs regardless of the particular color; however, recent experiments have found that many hosts respond more strongly to brown foreign eggs than to equally dissimilar blue eggs. Yet, none of these prior studies tested a brown-egg-laying species and, with only one exception, all were conducted in open nests where light levels are considered sufficient for effective color-based egg discrimination. Here, we explored how two cavity-nesting hosts of the parasitic brown-headed cowbird (Molothrus ater) - the blue-egg-laying eastern bluebird (Sialia sialis) and the brown-egg-laying house wren (Troglodytes aedon) - respond to experimental eggs painted six distinct colors ranging from blue to brown. Rejection responses of both hosts were best predicted by perceived differences in color between the model egg and their own eggs. Specifically, we found that house wrens preferentially rejected eggs bluer than their own eggs. However, although we found that bluebirds relied on perceived differences in color for their egg rejection decisions, further tests are needed to determine whether they preferentially rejected brown eggs or simply responded to absolute perceived differences in color. These findings demonstrate that these cavity-nesting birds treat perceived color differences in distinct ways, which has important implications on the coevolutionary arms races and the interpretation of avian-perceived color differences.

Adult sex ratio in south temperate house wrens is explained by sexual differences in adult survival

Adult sex ratio in south temperate house wrens is explained by sexual differences in adult survival

Highly Conserved Microchromosomal Organization in Passeriformes Birds Revealed via BAC-FISH Analysis

Passeriformes birds are widely recognized for their remarkable diversity, with over 5700 species described so far. Like most bird species, they possess a karyotype characteristic of modern birds, which includes a bimodal karyotype consisting of a few pairs of macrochromosomes and many pairs of microchromosomes. Although the karyotype is typically 2n = 80, the diploid number can atypically vary greatly, ranging from 56 to approximately 100 chromosomes. In this study, we aimed to understand the extent of conservation of the karyotype’s organizational structure within four species of this group using Bacterial Artificial Chromosomes via Fluorescence In Situ Hybridization (BAC-FISH) with microchromosome probes from Chicken (Gallus gallus) or Zebra Finch (Taeniopygia guttata) per microchromosomes (GGA10-28, except GGA16). By examining the chromosome complement of four passerine species—the Streaked Flycatcher (Myiodynastes maculatus), Shiny Cowbird (Molothrus bonariensis), Southern House Wren (Troglodytes aedon), and Double-collared Seedeater (Sporophila caerulescens)—we discovered a new chromosome number for Southern House Wren. Through FISH experiments, we were able to observe the same pattern of microchromosome organization as in the common ancestor of birds. As a result, we propose a new diploid number for Southern House Wren and confirm the conservation status of microchromosome organization, which may confer evolutionary advantages to this group.

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle