Eurasian Tree Sparrow Passer Montanus Research Articles

Behavioral responses to predator and heterospecific alarm calls are habitat-specific in Eurasian tree sparrows

Acoustic communication plays a vital role in predator-prey interactions. Although habitat structure has been shown to affect anti-predator tactics, little is known about how animals vary their behaviors in response to predator calls or heterospecific alarm calls in different environments. Here we used sound playbacks to test the responses of Eurasian tree sparrows (Passer montanus) foraging in harvested/unharvested rice paddy and open residential area. In the first experiment, we tested their behavioral responses to dove calls, male common cuckoo (Cuculus canorus) calls, hawk-like calls mimicked by female common cuckoo, sparrowhawk (Accipiter nisus) calls, and human yell calls produced to scare birds (predator signal playbacks). In the second experiment, we tested their behavioral responses to the Japanese tit’s (Parus minor) territorial songs and alarm calls (heterospecific alarm signal playbacks). Results showed that the tree sparrows had less fleeing in unharvested ripe rice paddy than in harvested rice paddy and open residential area. In predator signal playbacks, call type affected the escape behavior of sparrows in unharvested rice paddy and open residential area but not harvested rice paddy. In alarm signal playbacks, tit alarm calls evoked more fleeing than territorial songs in harvested rice paddy and open residential area but not unharvested rice paddy. These results suggest that anthropogenic habitat changes may influence avian anti-predator tactics.

Rewriting The Ugly Duckling tale: a Eurasian tree sparrow reared among great tits

Rewriting The Ugly Duckling Tale: a Eurasian tree sparrow reared among great tits. Competitive relationships between hole-nesting passerine bird species can lead to mixed broods when two or more species lay their eggs in the same nest. On 5 May 2023, during a routine inspection of nest boxes in orange plantations in Sagunto, Eastern Spain, we found a Eurasian tree sparrow (Passer montanus) egg dumped among nine great tit (Parus major) eggs. From this clutch, six great tits and the Eurasian tree sparrow hatched, and four great tits and the sparrow fledged. Using a video camera inside the nest box, we observed that the nestlings, including the sparrow, were fed only by great tit adults. The adults brought caterpillars, moths and spiders, a typical great tit nestling diet in this habitat. To date, great tit eggs have been found in Eurasian tree sparrow nests, but to our knowledge this is the first report of a Eurasian tree sparrow chick successfully raised by great tits.

A description of a new species of the genus Brachydistomum (Trematode, Dicrocoeliidae) from the Eurasian Tree Sparrow Passer montanus (Linnaeus) (Passeriformes) in Japan, with a report on the first intermediate host.

The trematode Brachydistomum suzume n. sp. (Dicrocoeliidae) was detected in the Eurasian Tree Sparrow Passer montanus, and described as a new species in Japan. This new species can be distinguished from the other members of the genus on the basis of morphological characters of suckers and reproductive organs. A partial sequence of adult mitochondrial cytochrome c oxidase subunit 1 (COI) was used as a DNA barcode, and dicrocoeliid sporocysts and cercariae detected from four camaenid land snail species, Bradybaena pellucida, Brad. similaris, Acusta sieboldiana and Euhadra brandtii, were molecularly identified as the new species. Phylogenetic trees of nuclear 28S ribosomal DNA and COI also showed the new species to be distinct from the other trematode species, including Brachydistomum spp.

Thermoregulation and antioxidant defense mechanisms in Eurasian tree sparrows (Passer montanus) under acute heat stress

Global warming has become an undeniable fact, and the frequent occurrence of extremely hot weather is a serious challenge to the survival of animals. As one of the most active components of the ecosystem, birds are sensitive to the constant changes in the climate and environment. To investigate the physiological responses of Eurasian tree sparrows (Passer montanus) to acute heat stress, various thermogenic parameters of the birds, which included resting metabolic rate (RMR), body mass, body temperature, water intake, and liver cellular metabolic capacity, were measured after exposure to 42°C for different times. The antioxidant response of Eurasian tree sparrows to heat stress was investigated by measuring the lipid oxidation indexes and related antioxidant oxidase activities in the serum and liver. Body temperature and water intake were significantly increased after 2 h of heat stress and lasted until the end of the heat stress (12 h). In contrast, RMR was significantly decreased after 2 h of heat stress. At the cellular level, liver COX activity was significantly increased during heat stress from 2 h to 6 h. Additionally, there was a significant increase in MDA content and superoxide dismutase (SOD) and catalase (CAT) activity levels in the serum. The glutathione peroxidase (GSH-PX) activity in the liver was significantly decreased after 2 h of heat stress. Our results indicated that heat production decreased while heat dissipation increased in Eurasian tree sparrows exposed to acute heat stress. At the same time, the internal antioxidant defense system of the birds was activated to counteract the damage caused by high temperatures. Therefore, it was reasonable to speculate that Eurasian tree sparrows might be resistant to high temperatures to the extent that they can maintain normal life activities through the regulation of thermogenic and antioxidant systems under acute heat stress.

Moderate mass loss enhances flight performance via alteration of flight kinematics and postures in a passerine bird.

Many birds experience fluctuations in body mass throughout the annual life cycle. The flight efficiency hypothesis posits that adaptive mass loss can enhance avian flight ability. However, whether birds can increase additional wing loading following mass loss and how birds adjust flight kinematics and postures remain largely unexplored. We investigated physiological changes in body condition in breeding female Eurasian tree sparrows (Passer montanus) through a dietary restriction experiment and determined the changes in flight kinematics and postures. Body mass decreased significantly, but the external maximum load and mass-corrected total load increased significantly after 3days of dietary restriction. After 6days of dietary restriction (DR6), hematocrit, pectoralis and hepatic fat content, take-off speed, theoretical maximum range speed and maximum power speed declined significantly. Notably, the load capacity and power margin remained unchanged relative to the control group. The wing stroke amplitude and relative downstroke duration were not affected by the interaction between diet restriction and extra load. Wing stroke amplitude significantly increased after DR6 treatment, while the relative downstroke duration significantly decreased. The stroke plane angle significantly increased after DR6 treatment only in the load-free condition. In addition, the sparrows adjusted their body angle and stroke plane angle in response to the extra load, but stroke amplitude and wingbeat frequency remained unchanged. Therefore, birds can maintain and even enhance their flight performance by adjusting flight kinematics and postures after a short-term mass loss.

Ecological value of wood energy plantations in the support of some animal groups

Today, some environmental problems have reached such severe proportions that it is no longer enough to recognise them, but environmentally friendly solutions must be used to reduce them. The reduction in the area of natural forests of native species is causing problems in several ways. This research aimed to highlight how environmental, conservation and economic interests can be reconciled. In addition to natural forests, wood energy plantations are becoming increasingly important. Energy import dependency is a problem for most countries, for which wood energy plantations can partly offer an alternative. Native forests can be protected, and their area increased where possible. Meanwhile, energy plantations can be established in areas with low agricultural productivity. In this experiment, I studied a plantation of Pedunculate Oak (Quercus robur), a Black Locust (Robinia pseudoacacia) and a Paulownia (Paulownia Shan Tong). I selected burrowing birds and ground-dwelling arthropods as indicator groups. I did this by establishing a nesting colony and soil trapping. I wanted to demonstrate that, in addition to natural forests, wood energy plantations have a role not only in economic terms but also in maintaining certain animal groups. Soil trapping tests were carried out in all three tree plantations. The obtained results showed that in the Paulownia plantation, the occupancy rate of nest boxes was almost 100%, while in the Black Locust plantation it was around 30%. Among the species that occupied the nesting sites, the Common Starling (Sturnus vulgaris) and the Eurasian Tree Sparrow (Passer montanus) were more abundant, while Great Tit (Parus major) was present in the Black Locust plantation. These are opportunistic species for which nesting opportunity is the most important factor, since their feeding area (in the case of the Common Starling and the Eurasian Tree Sparrow) is not typical of the nesting area. The soil trap investigations show that there are no significant differences in the composition of the arthropod group (beetles, spiders) in the study areas.

Responses of birds to observers holding popguns: Hunting history influences escape behavior of urban birds

Abstract Human activities affect bird behavior both directly and indirectly. Birds constantly regulate their behavior in response to human disturbance. Gun hunting, a major directional disturbance, puts enormous selection pressure on birds. In China, gun bans have been in place for nearly 30 years, and little hunting using guns occurs in modern cities. However, little attention has been paid to whether a history of hunting still affects the behavioral adaptations of urban birds. In this study, we compared the flight initiation distance (FID) of the Eurasian tree sparrow Passer montanus, Azure-winged magpie Cyanopica cyanus, Common hoopoe Upupa epops and Eurasian magpie Pica pica in the presence of observers with or without popguns. The Eurasian tree sparrow, Azure-winged magpie, and Eurasian magpie effectively recognized the difference between the observers, and perceived the armed observer as a greater threat, exhibiting earlier escape behavior, but this phenomenon was not found in the Common hoopoe. The different expressions in FID of experimental bird species in China cities may be affected by the different levels of recognition of hunting pressure due to different hunting histories.

Unusual foraging behaviour of the Bengal Slow Loris Nycticebus bengalensis (Lacépède, 1800) (Mammalia: Primates: Lorisidae) in the Shan Highlands, Myanmar

In April 2022, in northern Shan State, Myanmar, a Bengal Slow Loris Nycticebus bengalensis, an Endangered species, was observed entering a house and feeding on two Eurasian Tree Sparrows Passer montanus. This observation provides new information about the diet of Nycticebus bengalensis and its habituation to a highly disturbed urban environment.

The call type variation and usages of the Eurasian tree sparrow Passer montanus

Bird call, which is widely used in all species of birds, is short, simple, and functionally diverse in comparison to song. Here, we have recorded call types of Eurasian tree sparrows ( Passer montanus) at multiple situations and various communal behaviors. The Eurasian tree sparrow belongs to the oscine (song-learning) group of songbirds, but their calls are more developed than their song. The calls are used to communicate a variety of behaviors in their social flock. In this study, we categorized call types and usages in relation to the situation on the basis of visual categorization of spectrograms and descriptive measurements. Adult Eurasian tree sparrows have 9 call types (including 9 sub-types at A1 family) and chicks have one (including 2 sub-types). Each call type could be classified as A1 contact call, A2 Fight-intention call, A3 Aerial call, A4 Alarm/Anxiety call, A5 Emergency call, A6 Warning/Threat call, A7 Stimulate call, A8 Screaming call, A9 Social calling, and C1 Begging call. Our results suggest that the diversity of Eurasian tree sparrow’s call types is related to the complex social structure of the species, and might be associated to evolution of sociality. Further research on correlation between various call types and social behavior is needed to find social communication characteristics of Eurasian tree sparrows and other social weaver species with similar ecology may reveal whether evolutionary pressures of sociality lead to increased call complexity.

Long-Term Population Trends of House Sparrow and Eurasian Tree Sparrow in Spain

Urban areas are constantly increasing, which can cause an effect in bird populations since human activities lead to nature alterations. Populations of House Sparrow (Passer domesticus) and Eurasian Tree Sparrow (Passer montanus) have been decreasing in Spain according to the latest national censuses in Spain. In this study, we tried to assess the population trend over more than two decades using ringing data from Spanish constant effort sites, as well as to determine the population and breeding success proxy in relation to habitat composition at landscape level. We analysed the data and confirmed the decreasing trend in the two species. However, Eurasian Tree Sparrow showed signs of increasing presence in urban areas. Furthermore, the productivity remained stable over sampling sites and years, meaning that the causes of the decreasing populations are affecting both adult and juvenile individuals.

Susceptibility and Pathogenesis of Eurasian Tree Sparrows Experimentally Inoculated with Velogenic Newcastle Disease Virus.

Wild-caught Eurasian tree sparrows (Passer montanus) were experimentally inoculated with genotype VII velogenic Newcastle disease virus (NDV) APMV1/chicken/Japan/Fukuoka-1/2004 to investigate the susceptibility and pathogenesis of infected sparrows. Intranasal inoculation of two groups with high or low doses of the virus resulted in the mortality of some birds in both groups on days 7-15 postinoculation. Neurologic signs, ruffled feathers, labored breathing, emaciation, diarrhea, depression, and ataxia were observed in a few birds that eventually succumbed to death. The inoculation of the higher viral load resulted in higher mortality and hemagglutination inhibition antibody detection rates. Tree sparrows that survived the 18-day observation period after inoculation exhibited no apparent clinical signs. Histologic lesions in dead birds were observed in the nasal mucosa, orbital ganglion, and central nervous system, accompanied by NDV antigens detected by immunohistochemistry. Viral inclusion bodies were rarely observed in the cytoplasm of neurons. NDV was isolated from the oral swab and brain of dead birds but not from other organs, including the lung, heart, muscle, colon, and liver. In another experimental group, tree sparrows were intranasally inoculated with the virus and then examined 1-3 days later to examine the early pathogenesis of the disease. Inoculated birds exhibited inflammation of the nasal mucosa with viral antigens, and virus was isolated from some oral swab samples on days 2 and 3 postinoculation. The results of the present study suggest that tree sparrows are susceptible to velogenic NDV, and the infection could be fatal, although some birds can exhibit asymptomatic or mild infection. The unique pathogenesis regarding the neurologic signs and viral neurotropism of velogenic NDV was characteristic in infected tree sparrows.

Nest entry shape change may cause nest abandonment in urban cavity-nesting species: a case study of the Tree Sparrow Passer montanus

The threat of predation is the main cause of bird nest abandonment, with such behaviour imposing considerable energetic costs on breeding birds. However, for several species, nest abandonment can be a less costly alternative to complete brood failure. In this study, we examined nest abandonment among Eurasian Tree Sparrows (Passer montanus) by surveying 71 Tree Sparrow nests with various types of entry holes and conducted artificially manipulating some of the entrance shapes. We found that nest abandonment was caused by changes to the nest entry shape in seven cases and by human interference in two cases. Nest abandonments occurred throughout the breeding season, and breeding pairs attempted to breed again immediately after nest abandonment. The results of the artificial nest entry shape manipulation experiment showed that nine of twelve nests (75.0%) were abandoned where the nest entrance holes were widened, and six of eleven nests (54.5%) were abandoned where the nest entrance holes were narrowed. However, none of the nests were abandoned where the entry shape was unchanged. Thus, nest abandonment by Tree Sparrows is correlated with nest entry shape manipulation and is more likely to occur when the energy cost of breeding again is less than that of abandoning the nest.

Genetic Parent-Offspring Relationships Predict Sexual Differences in Contributions to Parental Care in the Eurasian Tree Sparrow

Negative relationships between the degree of parental investment and the presence of unrelated offspring in the nest due to extra-pair paternity (EPP) or conspecific brood parasitism (CBP) are predicted in monogamous species. This is because investing in unrelated offspring is costly to individual parents. However, such strategies may be adaptive for one social partner. Because parental investment changes in response to that by the social partner, the predicted relationship needs to be assessed empirically in wild animal populations, with consideration for male and female parental care. Furthermore, both EPP and CBP must be considered simultaneously in such a study. In this study, we tackled the issue using the semi-colonial Eurasian Tree Sparrow Passer montanus, in which both EPP and CBP were predicted to occur. We tested whether there is a negative relationship between the degree of parental care of both males and females and the presence of EPP or CBP, taking into consideration the parental investment of their social partners, using behavioral observations and parentage analyses based on seven microsatellite loci. The results revealed a moderately high frequency of EPP and CBP within a sparrow colony. A negative relationship between parental care by the social male parent and the presence of EPP was suggested, while this was possibly as a result of the increase in parental investment by their female partner. CBP was also inferred to be linked with male parental investment, while females may have compensated for the cost of CBP in their provisioning efforts by egg rejection. High frequencies of occurrence of both EPP and CBP allowed us to shed light on how parental investment is related to the presence of unrelated young in the complex social system of the Eurasian Tree Sparrow.

Gut microbiome composition associated with Plasmodium infection in the Eurasian tree sparrow

Recent expansion of microbiome research has uncovered connections between resident microbial communities and blood parasite risk, establishing the potential for microbial disease treatments such as probiotics in the future. However, this field has largely focused on humans and model organisms, leaving much unknown about how microbial communities might directly or indirectly impact parasite infection in wild populations and non‐mammals. To contribute to this knowledge base in wild birds, we collected fecal and blood samples from wild Eurasian tree sparrows (Passer montanus) in the United States to test for associations between blood parasite infection and the gut microbiome. We used a widespread molecular approach to test 81 samples from peripheral blood for Plasmodium and Haemoproteus, and we characterized the gut microbiome using fecal samples as a proxy. Neither alpha nor beta diversity significantly varied with detected Plasmodium infection. However, differential abundance analysis highlighted a number of significantly varying bacteria, with the greatest representation within the phyla Proteobacteria and Firmicutes in Plasmodium‐infected birds. These differentially abundant taxa offer a starting point for experimental work establishing the relationship between microbial abundance and Plasmodium infection.

Evolutionary relationships of mitogenomes in a recently radiated Old World avian family

Environmentally heterogeneous mountains provide opportunities for rapid diversification and speciation. The family Prunellidae (accentors) is a group of birds comprising primarily mountain specialists that have recently radiated across the Palearctic region. This rapid diversification poses challenges to resolving their phylogeny. Herein we sequenced the complete mitogenomes and estimated the phylogeny using all 12 (including 28 individuals) currently recognized species of Prunellidae. We reconstructed the mitochondrial genome phylogeny using 13 protein-coding genes of 12 species and 2 Eurasian Tree Sparrows (Passer montanus). Phylogenetic relationships were estimated using a suite of analyses: maximum likelihood, maximum parsimony and the coalescent-based SVDquartets. Divergence times were estimated by implementing a Bayesian relaxed clock model in BEAST2. Based on the BEAST time-calibrated tree, we implemented an ancestral area reconstruction using RASP v.4.3. Our phylogenies based on the maximum likelihood, maximum parsimony and SVDquartets approaches support a clade of large-sized accentors (subgenus Laiscopus) to be sister to all other accentors with small size (subgenus Prunella). In addition, the trees also support the sister relationship of P. immaculata and P. rubeculoides ​+ ​P.atrogularis with 100% bootstrap support, but the relationships among the remaining eight species in the Prunella clade are poorly resolved. These species cluster in different positions in the three phylogenetic trees and the nodes are often poorly supported. The five nodes separating the seven species diverged simultaneously within less than half million years (i.e., between 2.71 and 3.15 million years ago), suggesting that the recent radiation is likely responsible for rampant incomplete lineage sorting and gene tree conflicts. Ancestral area reconstruction indicates a central Palearctic region origin for Prunellidae. Our study highlights that whole mitochondrial genome phylogeny can resolve major lineages within Prunellidae but is not sufficient to fully resolve the relationship among the species in the Prunella clade that almost simultaneously diversify during a short time period. Our results emphasize the challenge to reconstruct reliable phylogenetic relationship in a group of recently radiated species.

Feed Preference, Adaptation, and Role of The Eurasian Tree Sparrows (Passer Montanus L.) in Urban and Rural Environments

The Eurasian tree sparrow (Passer montanus L.) known as both pest and predators; in the urban area, it is considered a pest because of its droppings, feathers, and nests around the house. Meanwhile, in rural areas, it is considered both pests and predators because their diets are small insects and small grains like a grain in the rice field. This study aimed to determine the daily consumption rate of sparrows on grain; their preferred food; identify the adaptability; and the role of sparrows in urban and rural areas. Feeding ability test using the no-choice baiting method. Food preference test using the choice baiting method. The adaptability and role of sparrow data are obtained through location determination and direct observation in the field. The results show that the consumption rate of individual sparrow is ten percent of body weight. The most preferred food for sparrow is yellow mealworm, followed by millet, cricket, foxtail millet, rice grain, and corn. The Eurasian tree sparrow is not considered a pest on rice fields. The presence of the sparrow in urban areas is less than in rural areas. Both in urban and rural areas, more sparrows were seen or found in the morning than in the afternoon. Sparrows can adapt well in rural and urban areas because the environment provides open area and house building. In urban areas, sparrow is considered urban pests; meanwhile in rural areas they potentially considered a pest on barley and millet, and predators on small insects.

Discriminant Criteria for Field Sexing in the Eurasian Tree Sparrow by Combining Body Size and Plumage Features

The Eurasian tree sparrow (Passer montanus) is a monomorphic passerine, for which it is impossible to differentiate between males and females based on external characteristics. Being a species frequently captured for ringing, having a reliable method to determine sex from conventional biometric measurements would facilitate its study and be very useful for the correct management and conservation of this declining species. In the present study, we used biometric measurements recorded in 66 individuals captured with mist nets in communal roosts in northern Spain during the winter and sexed them using molecular techniques. We conducted a discriminant function analysis (DFA) to derive equations that allowed us to determine the sex of the specimens from some of the measurements recorded in the field. Significant differences were found between males and females in wing length, third primary length, badge width and height and body weight. The DFA provided two functions that correctly classified the sex of 94.7% of the individuals using wing length and badge width, and 98.2% if weight was added to the analysis. Our results allow sexing from measurements that can be easily recorded in the field with the tools commonly used in banding sessions and without the need for additional training. Considerations of Bergmann’s and Allen’s rules on body size and the use of DFA in different populations are discussed.

Space use of wintering Eurasian Tree Sparrows (Passer montanus) in a semi-urban area: a radiotelemetry-based case study

Abstract Space use, which includes the home range and habitat utilisation pattern of individuals for different activities (e.g. foraging, roosting), is one of the fundamental aspects of a species ecology. Hence, knowledge on the different aspects of space use in general is essential to understand the relationship between species and their habitat. Here, we investigated the home range size (using the minimum convex polygon method; MCP) and roosting site selection, using radiotelemetry, in a sedentary passerine species, the Eurasian Tree Sparrows (Passer montanus). The study was carried out during the non-breeding period (i.e. wintering), in a semi-urban habitat where supplemental feeding was also available. We found that individuals had highly variable home ranges, both in shape and size (mean ± SD of 95% MCP: 6.89 ± 5.73 ha), the location of which was influenced by the presence of bird feeders. Roosting sites of the tracked individuals were largely consistent at an individual level, that is, all birds used the same locations for roosting during the whole tracking period, and the roosting sites of all individuals were located on buildings, except for a few rare occasions. Our results suggest that urbanised habitats can provide multiple benefits for the individuals during the winter in the form of easily accessible resources (e.g. food, roosting place), and individuals readily exploit these resources by adjusting their space use according to their availability.

Effects of Valley Topography on Acoustic Communication in Birds: Why Do Birds Avoid Deep Valleys in Daqinggou Nature Reserve?

To investigate the effects of valley topography on the acoustic transmission of avian vocalisations, we carried out playback experiments in Daqinggou valley, Inner Mongolia, China. During the experiments, we recorded the vocalisations of five avian species, the large-billed crow (Corvus macrorhynchos Wagler, 1827), common cuckoo (Cuculus canorus Linnaeus, 1758), Eurasian magpie (Pica pica Linnaeus, 1758), Eurasian tree sparrow (Passer montanus Linnaeus, 1758), and meadow bunting (Emberiza cioides Brand, 1843), at transmission distances of 30 m and 50 m in the upper and lower parts of the valley and analysed the intensity, the fundamental frequency (F0), and the first three formant frequencies (F1/F2/F3) of the sounds. We also investigated bird species diversity in the upper and lower valley. We found that: (1) at the distance of 30 m, there were significant differences in F0/F1/F2/F3 in Eurasian magpies, significant differences in F1/F2/F3 in the meadow bunting and Eurasian tree sparrow, and partially significant differences in sound frequency between the upper and lower valley in the other two species; (2) at the distance of 50 m, there were significant differences in F0/F1/F2/F3 in two avian species (large-billed crow and common cuckoo) between the upper and lower valley and partially significant differences in sound frequency between the upper and lower valley in the other three species; (2) there were significant differences in the acoustic intensities of crow, cuckoo, magpie, and bunting calls between the upper and lower valley. (3) Species number and richness were significantly higher in the upper valley than in the lower valley. We suggested that the structure of valley habitats may lead to the breakdown of acoustic signals and communication in birds to varying degrees. The effect of valley topography on acoustic communication could be one reason for animal species avoiding deep valleys.

Life history variation between two Eurasian tree sparrow Passer montanus populations at different altitudes

Abstract Altitudinal gradients create environmental variation that can strongly affect avian life history strategies. To fully understand this issue, a comparison of the demography of populations of the same species over large altitudinal differences is required. Here, we investigated the breeding ecology of two populations of Eurasian tree sparrow (Passer montanus), one in the temperate zone of central China at an altitude of 30 m and another in the alpine zone of the northeastern Tibetan plateau at an altitude of 3430 m. The breeding ecology of this species was rarely studied at such a high altitude before. Our result revealed that high-altitude tree sparrows started breeding later, had a shorter breeding period (80 versus 140 days), produced smaller broods (1.2 versus 2.5 chicks) and had significantly smaller clutches (4.0 versus 4.9 eggs) but larger eggs (4272 versus 3443 mm3) when compared with their low-altitude counterparts. Besides, tree sparrows at our high-altitude site had longer nestling periods (14.5 versus 13.4 days) than those at the low-altitude site. High-altitude tree sparrows tend to have reduced fecundity but allocate more energy into each offspring to confront the stressful conditions at high altitudes. The observed patterns are consistent with adaptive life history strategies.