The incubation patch of the house sparrow, Passer domesticus Linnaeus

Does environmental metal pollution affect bird morphometry? A case study on the tree sparrow Passer montanus

Morphological characteristics are the leading indicators of the health status of birds. To explore the effects of heavy metals on bird morphometry in natural populations, tree sparrows (Passer montanus) were studied in a polluted site [Baiyin (BY)] and a relatively unpolluted site [Liujiaxia (LJX)]. This study aimed to examine whether morphological variables, the fluctuating asymmetry (FA) of the wing, tarsus, and toe length, were associated with heavy metals (Cu, Zn, Pb, and Cd) and Ca levels in different tissues and feces of adults and nestlings. Results showed that adults collected from BY contained relatively higher heavy metal concentrations and lower Ca concentrations in different tissues than those from LJX. Smaller body sizes and higher FA levels of adults and nestlings were found in BY than in LJX. Although higher heavy metal concentrations in some tissues were associated with smaller morphological characteristics of adults, the effects were not obvious in nestlings. The most correlated heavy metal with as many characteristics was heavy metal in primary feather in both sites, and the most affected characteristic was body mass in BY. The FA values of adults and nestlings in BY were positively affected by heavy metal concentrations in different tissues and feces. The growth rate of wing and tarsus length of nestlings in BY were negatively affected by the FA values of wing and tarsus length, respectively. Taken together, environmental metal pollution might affect the morphological characteristics of tree sparrows. These findings suggest that the morphological characteristics of tree sparrows, especially FA, can be used as indicators of metal pollution, underscoring the importance of measuring morphological characteristics in avian ecotoxicology field studies.

Variation in sperm morphology and performance in tree sparrow (Passer montanus) under long-term environmental heavy metal pollution

Sperm morphology and performance traits are key determinants of male fertilization success, particularly when females copulate with multiple males. Such sperm traits have been reported to be influenced by environmental pollutants in various animals; however, such studies remain rare in free-living birds exposed to heavy metal pollution. In the present study, we selected tree sparrow (Passer montanus) as the study object to explore the effect of long-term environmental heavy metal pollution on sperm morphology (assessed mainly by using the dimensions of different sperm components and the sperm abnormality rates) and sperm performance (indicated by sperm velocity), and to elucidate potential relationships between variations in sperm morphology and performance. Sperm ATP concentration was also assessed considering sperm morphology and performance could be linked via energy availability. According to our results, tree sparrows from heavy metal polluted area (1) accumulated cadmium at a higher level in their testes; (2) produced longer sperm with lower abnormality rates, in addition to sperm with longer flagella and smaller head/flagellum ratios; (3) their sperm swam faster compared to those from the relatively unpolluted area, while no differences were observed in sperm ATP concentrations. We also found that the levels of lead and cadmium in testes affected the sperm nucleus length, and the level of copper in testes was negatively related to the proportions of abnormal sperm. Furthermore, the present study showed that sperm velocity was negatively correlated with sperm head lengths, head/flagellum ratios and ATP concentrations. Our study results reveal that sperm morphology and performance in tree sparrows show positive variations to maximize male fertility ability under long-term environmental heavy metal pollution, where males increase sperm flagellum lengths to decrease head/flagellum ratios, as opposed to varying sperm energy production, to achieve higher sperm velocity.

Effects of environmental metal pollution on reproduction of a free-living resident songbird, the tree sparrow (Passer montanus)

Anthropogenic metal pollution is known to adversely affect bird reproduction; however, few systematic studies are available on the effects of metal pollution on breeding performance and parental investment in a common resident songbird, the tree sparrow (Passer montanus). We conducted this study in two sites, a long-term heavy metal polluted site (Baiyin [BY]) and a relatively unpolluted site at approximately 110 km distance (Liujiaxia [LJX]), to assess the potential effects of environmental metal contamination on breeding parameters (clutch size, hatching success, fledging success, and growth of nestlings) and parental investment. The results showed smaller clutch size, lower fledging success, and differences in incubation behaviors of tree sparrows in BY than in LJX. Although there was no difference in parental body condition (residual body mass) between the two study sites, the parents responded differently with respect to reproduction due to varying metal levels in their habitats and bodies. Higher Cd levels in the primary feathers of females in BY were associated with lower clutch sizes. Parental investment including incubation duration and feeding rates showed no significant difference between the two sites during the incubation and nestling periods, but the frequencies of incubation visits were higher in BY. Parental behavior during the incubation period was also negatively affected by the parental Pb and Cd levels. Although the nestling growth patterns were relatively similar between the two sites, the nestlings were smaller, had lower body weight, and fledged later and fledging rate was also lower in BY than in LJX. Metal concentrations were higher in nestling organs and feces in BY. Taken together, metal pollution might adversely affect nestling growth condition. Our results suggest a negative response in the reproduction of tree sparrows to long-term environmental metal pollution.

Hypothalamus-pituitary-adrenal axis activity and the subsequent response to chronic stress differ depending upon life history stage

The hypothalamus-pituitary-adrenal (HPA) axis is modulated seasonally in many species, and chronic stress can alter HPA functioning. However, it is not known how these two factors interact - are there particular life history stages when animals are more or less vulnerable to chronic stress? We captured wild house sparrows (Passer domesticus) in Massachusetts during six different life history stages: early and late winter, pre-laying, breeding, late breeding, and molt. At each time point, we tested HPA function by measuring baseline and stress-induced corticosterone (CORT), negative feedback in response to an injection of dexamethasone, and maximum adrenal response through an injection of adrenocorticotropic hormone. We then brought birds into captivity as a model for chronic stress, and repeated the four tests 5 days later. At capture, all HPA variables varied seasonally. Birds showed increased negative feedback during breeding and late winter compared to pre-laying. Furthermore, birds during the late breeding period had down-regulated their HPA axis, perhaps in preparation for molt. After 5 days of captivity, house sparrows lost ∼11% of initial body mass, although birds lost more weight during molt and early winter. Overall, captive sparrows showed elevated baseline CORT and increased negative feedback, although negative feedback did not show a significant increase during any individual life history stage. During most of the year, adrenal sensitivity was unaffected by captivity. However, during late breeding and molt, adrenal sensitivity increased during captivity. Taken together, these data provide further support that HPA function naturally varies throughout the year, with the interesting consequence that molting birds may potentially be more vulnerable to a chronic stressor such as captivity.

The effect of clomiphene-citrate on broody turkey hens

The effect of clomiphene-citrate (CC) on broody turkey hens was examined in three experiments. Turkey hens were categorized as broody if found in the laying nest during 6 successive checks per day, if they were reluctant to leave the nest for a period of 24 hr or more, if they had ruffled feathers, and if their cloacal orifices were contracted so as to prevent vaginal exposure by abdominal massage during artificial insemination. In each experiment, 20 hens, selected as broody from commercial breeding flocks, were treated; half were treated with CC at a dosage of 6 mg/kg body weight/day (per os) for 5 consecutive days, and the rest (control) received parallel treatment with a placebo (CaCO3). In all experiments, the CC administration alleviated brooding behavior and increased egg production.

Density of arteriovenous anastomoses in some skin areas of the domestic fowl (Gallus domesticus)

The vascularity and the density of arteriovenous anastomoses (AVAs) were studied in the skin of the domestic fowl by using vascular injections and histological sections. The density of AVAs and associated blood vessels were low in the wattles and in the thoracic skin (five to 23 AVAs per cm2 and five to 14 AVAs per cm2, respectively), whereas the eyelids were highly vascular and contained many AVAs (170-172 AVAs per cm2). It is suggested that the blood vessels in the eyelids are important in the temperature regulation of the eye and that AVAs in the thoracic skin may contribute to the control of blood flow through the brood patch.