Summer Birds Research Articles

The Flame of the Forest (Butea monosperma) and its Mutualistic Interaction with Birds in Summer from Jamkhed Tahsil, Dist. Ahmednagar.

The flame of the forest (Butea monosperma), a species native to the Indian subcontinent, play a vital role in supporting biodiversity, particularly in its interactions with avian species in rural and semi-arid areas like Jamkhed tahsil in Ahmednagar district, Maharashtra. This study aims to explore the avian fauna of Jamkhed and the importance of butea monosperma in sustaining bird populations during summer season. We emphasize conservation efforts and ecological singnificance by highlighting the relationships between the region’s flora and fauna through this investigation. Field surveys were conducted during early morning and late afternoon from February-April 2024.Total 56 bird species was recorded. Through field observation explores the butea monosperma role as a food source, nesting and roosting habitat for birds. Result highlight that Butea monosperma is a keystone species in supporting avian population by providing nector during the dry season, shelter for nesting and promoting ecological balance through bird-mediated pollination. Birds contribute to the genetic diversity of Butea monosperma by facilitating cross-pollination between individual trees. This interaction ensures the tree's reproductive success and enhances its ability to regenerate and persist in the ecosystem.

Peak beta diversity occurs at regional spatial grains

Beta diversity (β) quantifies the dissimilarity between communities and is thus fundamental to biogeography and spatial ecology. However, multiple and conflicting hypotheses exist to explain how β varies with spatial scale (here grain within a constant extent). Some resolution on spatial scaling of β may help clarify long-standing debate about: (a) β itself and (b) the ecological community concept, because the clearest spatial size of an ecological community corresponds to the scale with maximal β. Here we test five alternative hypotheses for β spatial scaling by calculating β for four very different taxa (ants, birds, diatoms, and trees) at spatial grains ranging from one to one million km2 in a constant spatial extent (contiguous USA). We also test repeatability for: (a) summer and winter bird β in six consecutive years; (b) trees through time (4 years, spaced 5 years apart). Specifically, we organize point data into hexagonal polygons, and then calculate mean pairwise β between each hexagon and its neighbors. We also calculate the deviation of β from two null models (assuming either spatial heterogeneity or homogeneity). For multiple reasons, β deviation based on spatial heterogeneity was preferable to that based on spatial homogeneity. For all taxa, β peaks at regional scales: trees ~300 km2; winter birds ~500 km2; summer birds ~2000 km2; ants ~2000 km2; diatoms ~11,000 km2. Also, spatial scaling is consistent inter-annually (birds, trees) and sensitive to seasonality (birds). Results broadly support the regional community concept and, based on the variety of taxa evaluated here, similar patterns are likely across the tree of life. Local ecological and evolutionary forces scale up to form regional community patterns and results here support efforts to coordinate local conservation efforts in regions (e.g., corridors and networks) to best conserve biodiversity. Beta diversity peaked at substantial spatial scales for all taxa evaluated here (ants, birds, diatoms, trees), suggesting a general pattern. The regional community concept advanced by Robert Ricklefs is supported empirically, in preference to four other hypotheses also tested. Beta diversity calculations used a relatively new deviation from a spatially heterogeneous null, which modestly adjusted observed beta diversity. Results support use of this newer beta deviation rather than the older beta deviation based on spatial homogeneity. Given that ecological communities appear regional in scale, local biodiversity conservation work can best ensure success if it is regionally coordinated.

Intestinal microbiota of Nearctic-Neotropical migratory birds vary more over seasons and years than between host species.

Seasonal migration of Nearctic-Neotropical passerine birds may have profound effects on the diversity and abundance of their host-associated microbiota. Migratory birds experience seasonal change in environments and diets throughout the course of the annual cycle that, along with recurrent biological events such as reproduction, may significantly impact their microbiota. In this study, we characterize the intestinal microbiota of four closely related species of migratory Catharus thrushes at three time points of their migratory cycle: during spring migration, on the summer breeding territories and during fall migration. Using observations replicated over 3 years, we determined that microbial community diversity of Catharus thrushes was significantly different across distinct time periods of the annual cycle, whereas community composition was more similar within than across years. Elevated alpha diversity in the summer birds compared to either migratory period indicated that birds may harbour a reduced microbiota during active migration. We also found that community composition of the microbiota did not substantially differ between host species. Finally, we recovered two phyla, Cyanobacteria and Planctomycetota, which are not commonly described from birds, that were in relatively high abundance in specific years. This study contributes to our growing understanding of how microbiota in wild birds vary throughout disparate ecological conditions and reveals potential axes across which an animal's microbial flexibility adapts to variable environments and recurrent biological conditions throughout the annual cycle.

Mobbing behavior of songbirds in response to calls of an ambush-predator, the Northern Pygmy-Owl

Mobbing is a widespread but risky behavior where prey actually approach and may even attack their predators. Small songbirds gather in multi-species flocks to direct mobbing at birds of prey such as the Northern Pygmy-Owl (Glaucidium gnoma), a small diurnal species of owl in mountainous western North America. We hypothesized that intensity of mobbing behavior would vary according to risk to songbirds and that risk varied seasonally and across elevations. In particular, we expected mobbing intensity to change seasonally as a function of two primary sources of risk: seasonal dietary changes of pygmy-owls and distribution of pygmy-owls as a function of elevation. Pygmy-owls are known to shift their diet from mostly mammals in early spring to birds in early summer, so we hypothesized risk of predation would vary in parallel. Likewise, risk was expected to vary as the distribution of pygmy-owls was thought to vary seasonally across elevations. To elicit mobbing in a controlled manner, we conducted owl call playback experiments in the Oregon Coast Range mountains, United States. Overall, we found mobbing to be rare, observing it in 8.1% of 663 experiments. The frequency of mobbing did not appear to vary across elevations. Instead, mobbing varied mostly by season. The frequency of mobbing was highest during fall at lower elevations. Mobbing was rarest (1.3% of trials) during winter. Mobbing occurred during seasons when pygmy-owls tend to consume more birds, consistent with the hypothesis that seasonal variation in risk influences mobbing. In our study, mobbing happened when risk was higher. However, the increased risk may be offset by the influence of mobbing group size. Mobbing was more likely to occur at sites where the number of songbirds, especially chickadees (Poecile sp.) and nuthatches (Sitta sp.), was larger. Yet, even when songbird numbers were high, mobbing was rare during winter, suggesting an interaction between risk and energetic costs of mobbing. Additional experiments manipulating food resource availability may be able to reveal the strength and influence of the interaction on mobbing decisions.

Remotely Sensed Winter Habitat Indices Improve the Explanation of Broad-Scale Patterns of Mammal and Bird Species Richness in China

Climate change is transforming winter environmental conditions rapidly. Shifts in snow regimes and freeze/thaw cycles that are unique to the harsh winter season can strongly influence ecological processes and biodiversity patterns of mammals and birds. However, the role of the winter environment in structuring a species richness pattern is generally downplayed, especially in temperate regions. Here we developed a suite of winter habitat indices at 500 m spatial resolution by fusing MODIS snow products and NASA MEaSUREs daily freeze/thaw records from passive microwave sensors and tested how these indices could improve the explanation of species richness patterns across China. We found that the winter habitat indices provided unique and mutually complementary environmental information compared to the commonly used Dynamic Habitat Indices (DHIs). Winter habitat indices significantly increased the explanatory power for species richness of all mammal and bird groups. Particularly, winter habitat indices contributed more to the explanation of bird species than mammals. Regarding the independent contribution, winter season length made the largest contributions to the explained variance of winter birds (30%), resident birds (27%), and mammals (18%), while the frequency of snow-free frozen ground contributed the most to the explanation of species richness for summer birds (23%). Our research provides new insights into the interpretation of broad-scale species diversity, which has great implications for biodiversity assessment and conservation.

Ege Denizi’nde kıyı balıkçılığı ve deniz kuşları arasındaki bazı etkileşimler

In this study, it is aimed to determine the some interactions between various fishery types and seabirds, results of this interaction and sea bird species that have been interacting due to secondary attraction factors. A total of 80 fishermen, working in fish farms, small scale fishery (SSF) and lagoons located in Izmir, Aydın and Muğla were face-to-face interviewed between September 2016 and December 2018. The great cormorant (Phalacrocorax carbo), yellow-legged gull (Larus michahellis), great white egret (Ardea alba), some yelkouan shearwater (Puffinus yelkouan) and great white pelican (Pelecanus onocrotalus) are the bird species that have an interaction with coastal fishermen and sea-cage fish farms. 82% of employees in sea-cage fish farms mentioned that they have an interaction with sea birds in winter, besides %50 of SSF have an interaction with sea birds in summer. The difference between interaction rate according to seasons has been found as statistically significant (p<0.05). 33% of employees in fish farms expressed that they see sea birds during the day. This ratio is 21.7% and 15% for SSF and fishermen in lagoon, respectively. Furthermore, 8.3% of fishermen in lagoon, 11% of employees in fish farms and SSF mentioned that they have an interaction with seabirds especially in the morning time.

Sleep Time in the European Starling Is Strongly Affected by Night Length and Moon Phase.

Sleep is considered to be of crucial importance for performance and health, yet much of what we know about sleep is based on studies in a few mammalian model species under strictly controlled laboratory conditions. Data on sleep in different species under more natural conditions may yield new insights in the regulation and functions of sleep. We therefore performed a study with miniature electroencephalogram (EEG) data loggers in starlings under semi-natural conditions, group housed in a large outdoor enclosure with natural temperature and light. The birds showed a striking 5-h difference in the daily amount of non-rapid-eye-movement (NREM) sleep between winter and summer. This variation in the amount of NREM sleep was best explained by night length. Most sleep occurred during the night, but when summer nights became short, the animals displayed mid-day naps. The decay of NREM sleep spectral power in the slow-wave range (1.1-4.3Hz) was steeper in the short nights than in the longer nights, which suggests that birds in summer have higher sleep pressure. Additionally, sleep was affected by moon phase, with 2h of NREM sleep less during full moon. The starlings displayed very little rapid-eye-movement (REM) sleep, adding up to 1.3% of total sleep time. In conclusion, this study demonstrates a pronounced phenotypical flexibility in sleep in starlings under semi-natural conditions and shows that environmental factors have a major impact on the organization of sleep and wakefulness.

Influence of seasonal climatic factors on the dynamics of birds interactions with linden consortia

The article is devoted to the bird communities in individual linden consortia (Tilia cordata Mill.) of the linden-ash oak forests. This work material was collected during different seasons of the 2009–2017 years in a linden-ash oak grove on the test plot No. 209 of the ecological profile of the NSC «Bel'gard Prisamar`e International Biospheric stationary», Novomoskovsk district, Dnepropetrovsk region. The individual consortia of 145 examples of three age conditions oak trees (virgins – virg, young generative – gl, mature and old generative individuals – g2-g3) has been investigated. Studies have shown that birds are actively involved in consortia of linden for most of the year. Meroconsortia of linden generative organs are attractive to birds during the growing season and in the cold season. In summer, the consortia of linden in terms of species composition of birds is inferior to the consortia of oak about 2 times. The same trend is observed in DTB and DMB. Only 2 species of birds participate in the consortia of the virgin linden. The consortia of young generative linden consists of only 4 species of birds, but DTB increases almost 30 times. The consortia of mature and old generative linden acquires a sufficient species composition – 14 species of birds. Interactions of birds with virginal linden are stochastic in autumn. Only 2 species of birds participate in the consortia of virgin linden in autumn. The consortia of young generative linden consists of 5 species (more than in summer). The old generative linden has a depression of consortia interactions of birds. Their volume is reduced by half compared to summer. Specialized consumers of linden nuts remain in the consortia of old generative linden mainly. Birds have very low DTB and DMB rates in consortia of all linden age groups in winter. Instead, the species composition of birds increases in the consortia of generative groups of linden in winter. The system of consortia interactions of birds is not intensive, but stable on the linden tree in winter. The volume of interactions of birds with a linden tree essentially increases in the spring. This trend is typical for trees with a dense crown. The number of consort birds is higher than in summer in consortia of virgin and young generative linden. DTB is five times higher in virgin linden than in summer. The participation of birds in the consortia of young generative linden is also greater than in summer. We believe that this is due to the fact that linden begins to grow earlier than other trees in the upper tier. The old generative linden is one of the main feeding grounds for birds in the spring. Linden, like common oak, is much more interesting for birds in spring and summer in contrast to field maple and ash. Linden first supports the system of trophic connections, and then topical in most seasons of the year. Linden forms stable groups of birds at a young generative stage during the year. Linden creates an environment for birds to live in the middle tier and complements the field maple.

Systematic prey preference by introduced mice exhausts the ecosystem on Antipodes Island

House mice (Mus musculus) are a widespread invasive species on islands. Where they are the sole introduced mammal they can have particularly strong negative impacts on recipient ecosystems. House mice impacts have been documented on almost every component of the terrestrial ecosystem on Southern Ocean islands, including plants, invertebrates, birds and ecosystem function. We undertook a comprehensive study to determine the impacts of house mice on Antipodes Island, New Zealand. This study was done prior to mouse eradication to inform monitoring and restoration. We used invertebrate pitfall trapping on the main Antipodes Island and neighbouring mouse-free offshore islands together with mouse stomach contents and stable isotope analyses of mouse livers to examine dietary preferences. We identified directly impacted and consumed invertebrate Orders relative to their abundance and provided a comprehensive picture of resource flow and overlap in the invaded terrestrial ecosystem. The remote terrestrial ecosystem of Antipodes Island was tightly circumscribed with strong resource overlap. Mouse diet varied seasonally with resource availability, dominated by invertebrates and land birds in summer, and plants and seabirds in winter. Invertebrates that were preferentially preyed upon were Amphipoda, Lepidoptera and some species of Coleoptera. These patterns suggest the ecosystem is annually driven by a seasonal bottom-up resource pulse over summer, where mice are a selective predator, differentially preying on invertebrates relative to invertebrate abundance. Mice appear to be exhausting preferred prey as they systematically consume their way through the terrestrial ecosystem. Land bird diet also varied seasonally and some of these birds likely competed with mice for invertebrate prey. Eradication of mice from Antipodes Island should reduce the predation on invertebrates and reduce the effects of competition and predation on land birds. This should have flow-on effects to the abundance of invertebrates and endemic land bird sub-species of pipit and snipe.

Metabolic Flexibility in Response to Within-Season Temperature Variability in House Sparrows.

Synopsis The climatic variability hypothesis (CVH) posits that more flexible phenotypes should provide a fitness advantage for organisms experiencing more variable climates. While typically applied across geographically separated populations, whether this principle applies across seasons or other conditions (e.g., open vs. sheltered habitats) which differ in climatic variability remains essentially unstudied. In north-temperate climates, climatic variability in winter usually exceeds that in summer, so extending the CVH to within-population seasonal variation predicts that winter phenotypes should be more flexible than summer phenotypes. We tested this prediction of the within-season extension of the CVH by acclimating summer and winter-collected house sparrows (Passer domesticus) to 24, 5, and −10°C and measuring basal metabolic rate (BMR) and summit metabolic rate (Msum = maximum cold-induced metabolic rate) before and after acclimation (Accl). To examine mechanistic bases for metabolic variation, we measured flight muscle and heart masses and citrate synthase and β-hydroxyacyl coA-dehydrogenase activities. BMR and Msum were higher for cold-acclimated than for warm-acclimated birds, and BMR was higher in winter than in summer birds. Contrary to our hypothesis of greater responses to cold Accl in winter birds, metabolic rates generally decreased over the Accl period for winter birds at all temperatures but increased at cold temperatures for summer birds. Flight muscle and heart masses were not significantly correlated with season or Accl treatment, except for supracoracoideus mass, which was lower at −10°C in winter, but flight muscle and heart masses were positively correlated with BMR and flight muscle mass was positively correlated with Msum. Catabolic enzyme activities were not clearly related to metabolic variation. Thus, our data suggest that predictions of the CVH may not be relevant when extended to seasonal temperature variability at the within-population scale. Indeed, these data suggest that metabolic rates are more prominently upregulated in summer than in winter in response to cold. Metabolic rates tended to decrease during Accl at all temperatures in winter, suggesting that initial metabolic rates at capture (higher in winter) influence metabolic Accl for captive birds.

Composition of physiologically important fatty acids in great tits differs between urban and rural populations on a seasonal basis

Fatty acids (FA) have crucial functions in animals, affecting e.g. inflammatory responses, thermoregulation, and cell membrane fluidity. Diet and ambient temperature affect animals’ FA composition, which, in turn, may influence these physiological processes. Great tits (Parus major) −common in both urban and rural habitats− are mainly granivorous during winter and insectivorous during summer. These diets show pronounced differences in FA composition. Such variation has context-dependent effects on physiology, because the thermal environment, food availability, and levels of pro-inflammatory environmental stressors differ between urban and rural areas. Thus, we investigated how great tit plasma FA composition varied between urban and rural habitats and across seasons. Eight FAs differed between urban and rural birds. Among these, arachidonic acid (omega (ω)-6 polyunsaturated FA) with thermoregulatory and pro-inflammatory properties was more abundant in urban than rural birds in winter, whereas ω-3 FAs with anti-inflammatory properties were more abundant in rural birds. The difference in pro- and anti-inflammatory FAs suggest that the negative health effects that urban birds suffer from being exposed to higher levels of pollutants might be enhanced by an elevated inflammatory response. Eight FAs differed between winter and summer birds. This variation reflected the diet change: FAs common in seeds, e.g. oleic- and linoleic acid, were present in higher amounts in winter birds, whereas ω-3 polyunsaturated FAs that are common in caterpillars were more abundant in summer birds. Overall, a larger seasonal variation was seen among the urban birds. This study is the first to reveal a difference in FA composition between urban and rural populations for all animals studied to date. Future experiments should unravel the physiological implications of this variation, and ultimately, link its effects to fitness of animals with different physiological and dietary requirements in ur

Observations of the summer birds of Tukarak Island (Belcher Islands, Nunavut), Nastapoka Islands (Nunavut), and Lac Guillaume-Delisle (northern Quebec)

In a survey of land and water birds of Tukarak and Nastapoka Islands and Lac Guillaume-Delisle in summer 2011, we recorded 22 of the 30 species known to breed on the Belcher Islands, as well as five non-breeding species, and we observed 32 species in Lac Guillaume-Delisle. In all areas surveyed, we observed a total of 43 species: 10 waterfowl, 2 gallinaceous birds, 3 loons, 2 hawks, 3 shorebirds, 1 auk, 3 gulls, 2 falcons, and 17 songbirds. In this area of Hudson Bay, a number of species reach the southern or northern limit of their breeding distribution in eastern Canada. In light of the impact that climate change may have on bird distribution in northerly latitudes, the Belcher Islands and adjacent mainland areas could be particularly useful locations for monitoring changes in the breeding range of birds.

Inferring the Migratory Status of Woodland Birds using Ringing Data: The Case of a Constant-Effort Site Located in the Iberian Highlands

Understanding the spatiotemporal distribution of birds is crucial for effective management and conservation of their populations. However, we still have only limited knowledge not only of the wintering destinations of many Iberian breeding migrants but also of aspects as general as the migratory behaviour of the populations of many common avian species that breed in the Iberian highlands. We used bird-ringing data to shed light on the migratory status (migratory, partially-migratory or sedentary) of the breeding populations of 13 common species occurring year-round in a woodland located on an Iberian plateau (Garaio, Araba, Spain; 574 m.a.s.l.), where ringing activities have been carried out over the last 20 years. To assess the extent to which birds breeding on this site remain in the area during winter and/or are replaced by conspecifics coming from other areas, we analysed: (1) changes in relative abundance of birds between summer and winter, (2) the frequency of sedentary individuals (birds captured both in summer and winter period in the study area) in relation to the number of individuals captured only in summer (summer visitors) or in winter (wintering birds), and (3) variation in wing length among summer, wintering and sedentary birds. Our results revealed great variation among species in the intensity of migratory behaviour, and a general arrival of foreign conspecifics during the winter for most of the species studied. Likewise, our study represents an illustrative example of how long-term ringing can be used to shed light on the migratory status of bird populations.

Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds

IntroductionArtificial light-at-night is known to affect a broad array of behaviours and physiological processes. In urbanized bird species, light-at-night advances important biological rhythms such as daily cycles of activity/rest and timing of reproduction, but our knowledge of the underlying physiological mechanisms is limited. Given its role as chronobiological signal, melatonin is a strong candidate for mediating the effects of light-at-night.ResultsWe exposed urban and rural European blackbirds (Turdus merula) to two light treatments equal in photoperiod but with different light intensities at night. The control group was exposed to 0.0001 lux (almost darkness), while the experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds. We obtained diel profiles of plasma melatonin for all birds in summer (July) and winter (January), while simultaneously recording locomotor activity. Daily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn. In winter, the amount of activity before dawn in the light-at-night group correlated with changes in melatonin from midnight to late night: the greater the decrease in melatonin, the greater the amount of pre-dawn activity. Urban and rural birds responded similarly to light-at-night with respect to melatonin, but differed in their behaviour, with rural birds showing more locomotor activity than urban counterparts.ConclusionsThis study points to reduced melatonin release at night as a potential physiological mechanism underlying the advanced onset of morning activity of urbanized birds. Based on the pattern of melatonin secretion, we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights.

Ageing Wrens Troglodytes troglodytes using the barring pattern across remiges

Two different ageing criteria are in common use for Eurasian Wrens Troglodytes troglodytes under the BTO Ringing Scheme, and both have their adherents and detractors. The identification of moult limits after the partial post-juvenile moult is effective for most birds in late summer and autumn, but becomes more difficult as plumage wear and damage increases in spring. The number of pale spots on the fourth primary is also effective in British birds in autumn and winter, but intermediate birds are not uncommon and plumage wear also reduces its usefulness. This paper proposes a third method, using the barring pattern across the secondaries and inner primaries of the partly opened wing. In contrast to the two established methods above, this criterion is unaffected by plumage wear and damage, and remains easily recognisable throughout the year.

Summer use of Rice Fields by Secretive Marsh Birds in the Mississippi Alluvial Valley of Northeast Louisiana

Many secretive marsh bird (SMB) species nest within rice fields, yet in most regions we do not understand the extent to which these birds use such habitats. In the summers of 2007 and 2008, we investigated summer use of rice fields by SMBs in northeast Louisiana and evaluated the local (within 100 m) and landscape (within 1 km) habitat characteristics influencing site selection. We did not encounter any SMB species in 2007, but we encountered low densities of Ixobrychus exilis (Least Bitterns), Rallus elegans (King Rails), and Fulica americana (American Coots) in mid-July of 2008. It is unclear whether or not the birds we detected were actually breeding in the rice fields, or merely using them as late summer foraging areas. When we combined detections of all species, we found that probability of occupancy was positively influenced by the proportion of the local habitat dominated by flooded ditches containing herbaceous emergent vegetation. Ditches likely provide refuge and resource alternatives that may be particularly important to these birds in the late summer when rice fields are drained and harvested. However, given that SMBs were detected at less than 10% of the 72 rice fields we surveyed, it appears as though Mississippi Alluvial Valley rice fields contribute very little toward supporting SMB populations.

Effects of Individual Pre-Fledging Traits and Environmental Conditions on Return Patterns in Juvenile King Penguins

Despite the importance of early life stages in individuals' life history and population dynamics, very few studies have focused on the constraints to which these juvenile traits are subjected. Based on 10 years of automatic monitoring of over 2500 individuals, we present the first study on the effects of environmental conditions and individual pre-fledging traits on the post-fledging return of non-banded king penguins to their natal colony. Juvenile king penguins returned exclusively within one of the three austral summers following their departure. A key finding is that return rates (range 68–87%) were much higher than previously assumed for this species, importantly meaning that juvenile survival is very close to that of adults. Such high figures suggest little juvenile dispersal, and selection occurring mostly prior to fledging in king penguins. Pre-fledging conditions had a strong quadratic impact on juvenile return rates. As expected, cohorts reared under very unfavourable years (as inferred by the breeding success of the colony) exhibited low return rates but surprisingly, so did those fledged under very favourable conditions. Juvenile sojourns away from the colony were shorter under warm conditions and subsequent return rates higher, suggesting a positive effect of climate warming. The longer the post-fledging trip (1, 2 or 3 years), the earlier in the summer birds returned to their natal colony and the longer they stayed before leaving for the winter journey. The presence of juveniles in the colony was more than twice the duration required for moulting purposes, yet none attempted breeding in the year of their first return. Juvenile presence in the colony may be important for acquiring knowledge on the social and physical colonial environment and may play an important part in the learning process of mating behaviour. Further studies are required to investigate its potential implications on other life-history traits such as recruitment age.

Season-Related Differences in the Biosynthetic Activity of the Neonatal Chicken Pineal Gland

Influence of the season of hatch on the functional characteristics of the pineal gland was examined in neonatal Hi-Line male chickens. The pineal glands from 2-day-old birds hatched in and winter, and kept from the day of hatch in artificial lighting conditions (12L:12D), were isolated under dim red light in the middle of the day or night. The pineal glands were analyzed to characterize their melatonin biosynthetic activity: (1) expression of the Arylalkylamine- N-acetyltransferase and Hydroxyindole-O-methyltransferase genes, encoding the final two enzymes of the melatonin biosynthesis pathway; (2) the activity of AA-NAT and HIOMT; and (3) the content of the main substrates of this pathway, tryptophan (TRY) and serotonin (5-HT). Daily changes in pineal AA-NAT activity were observed in chickens hatched in both seasons, with a more pronounced nocturnal increase in summer. In contrast, the level of Aa-nat gene expression, although exhibited the same nocturnal/diurnal pattern in both seasons, was much lower in the summer. The activity of HIOMT was season- and daytime-independent. In winter chickens the pineal content of 5-HT was low and stable, while in summer birds it was correlated with levels of AA-NAT activity and Aa-nat gene expression. TRY content was very high and exhibited neither daily nor seasonal changes. The pineal gland of newly hatched chickens kept in controlled 12L:12D conditions exhibits daily variations in melatonin biosynthetic activity influenced by the season. This suggests a maternal effect on the perinatal/postnatal development of the circadian clock residing in the chicken pineal gland.

Seasonal variation in the metabolism-temperature relation of House Sparrows ( Passer domesticus) in KwaZulu-Natal, South Africa

Many birds exhibit considerable phenotypic flexibility in metabolism to maintain thermoregulation or to conserve energy. This flexibility usually includes seasonal variation in metabolic rate. Seasonal changes in physiology and behavior of birds are considered to be a part of their adaptive strategy for survival and reproductive success. House Sparrows (Passer domesticus) are small passerines from Europe that have been successfully introduced to many parts of the world, and thus may be expected to exhibit high phenotypic flexibility in metabolic rate. Mass specific Resting Metabolic Rate (RMR) and Basal Metabolic Rate (BMR) were significantly higher in winter compared with summer, although there was no significant difference between body mass in summer and winter. A similar, narrow thermal neutral zone (25-28°C) was observed in both seasons. Winter elevation of metabolic rate in House Sparrows was presumably related to metabolic or morphological adjustments to meet the extra energy demands of cold winters. Overall, House Sparrows showed seasonal metabolic acclimatization similar to other temperate wintering passerines. The improved cold tolerance was associated with a significant increase in VO2 in winter relative to summer. In addition, some summer birds died at 5°C, whereas winter birds did not, further showing seasonal variation in cold tolerance. The increase in BMR of 120% in winter, compared to summer, is by far the highest recorded seasonal change so far in birds.

Seasonal Variation of Myostatin Gene Expression in Pectoralis Muscle of House Sparrows (Passer domesticus) Is Consistent with a Role in Regulating Thermogenic Capacity and Cold Tolerance

Winter acclimatization in small birds overwintering in cold climates, including house sparrows (Passer domesticus), is associated with improved cold tolerance, elevated summit metabolic rates (M(sum) = maximum cold-induced metabolic rate), and increased pectoralis muscle mass compared to summer birds. Myostatin is a potent autocrine/paracrine inhibitor of skeletal muscle growth in mammals and birds and is a potential candidate for regulation of seasonal phenotypic flexibility in birds. As a first step toward examining such a role for myostatin in small birds, we measured summer and winter gene expression of myostatin and its potential metalloproteinase activators TLL-1 and TLL-2 in house sparrows from southeastern South Dakota. Gene expression of myostatin decreased significantly in winter, with summer values exceeding winter values by 1.52-fold. Moreover, gene expression of TLL-1 was also significantly reduced in winter, with summer values exceeding winter values by 1.55-fold. These data are consistent with the hypothesis that the winter increases in pectoralis muscle mass, M(sum), and cold tolerance in house sparrows are mediated by reduced levels of myostatin and its activator TLL-1, and they suggest the possibility that myostatin may be a common mediator of phenotypic flexibility of muscle mass in birds.