The identification of sex in the starling Sturnus vulgaris using a molecular DNA technique

Female birds can be identified through the presence of a W-chromosome. We describe a procedure for amplifying a W-linked DNA marker in the starling (Sturnus vulgaris) by the polymerase chain reaction (PCR) so allowing the diagnosis of sex in this species. The technique is sensitive, allowing even the smallest chicks to be sexed from a blood sample. The method possesses a positive internal control to ensure accuracy. It is also applicable to the spotless starling (S. unicolor) but not to two bird species outside the genus. The nucleotide sequence of the female-specific PCR product is given.     

Starlings (Sturnus vulgaris) exploiting patches: response to long-term changes in travel time

In this paper we explore the way foraging animals integrateexperience over time. The marginal value theorem shows thatto maximize long-term gain rate, foragers should adjust patchexploitation to theaverage travel time for the habitat, andmany experiments do find a positive relationship between averagepatch exploitation and average interpatch travel time. Thisrelationship implies that animals use experience to determineforaging tactics but, by itself, does not imply that anythingbut the most recent experience (say, the time taken to findthe current patch) has an effect on behavior. We directly testedthe influence of events before the most recently experiencedtravel by examining adjustments in foraging behavior after stepwisechanges between two homogeneous environments, each with a singletravel distance. Using starlings (Sturnus vulgaris) in a closed-economylaboratory simulation of a patchy environment, we found thatduring periods of active foraging, the average number of preyper patch visit is in close agreement with that predicted forrate maximization. After changes in travel time, birds tookapproximately six full cycles of travel and patch use beforereaching a new asymptotic behavior. The pattern of adjustmentdid not vary with successive presentations of the environmentalchange. These results demonstrate that memory for more thanone travel episode is involved in the foraging decisions ofstarlings. We relate our results to apparently conflicting datafrom previous experiments and to models of memory and informationprocessing.     

Manipulating developmental stress reveals sex-specific effects of egg size on offspring phenotype

The general lack of experimental evidence for strong, positive effects of egg size on offspring phenotype has led to suggestions that avian egg size is a neutral trait. To better understand the functional significance of intra-specific variation in egg size as a determinant of offspring fitness within a life-history (sex-specific life-history strategies) and an environmental (poor rearing conditions) context, we experimentally increased developmental stress (via maternal feather-clipping) in the sexually size-dimorphic European starling (Sturnus vulgaris) and measured phenotypic traits in offspring across multiple biological scales. As predicted by life-history theory, sons and daughters had different responses when faced with developmental stress and variation in egg size. In response to developmental stress, small egg size in normally faster-growing sons was associated with catch-up growth prior to attaining larger adult size, resulting in a reduction in developmental stability. Daughters apparently avoided this developmental instability by reducing growth rate and eventual adult body mass and size. Interestingly, large egg size provided offspring with greater developmental flexibility under poor growth conditions. Large-egg sons and daughters avoided the reduction in developmental stability, and daughters also showed enhanced escape performance during flight trials. Furthermore, large egg size resulted in elevated immune responses for both sexes under developmental stress. These findings show that there can be significant, but complex, context-specific effects of egg size on offspring phenotype at least up to fledging, but these can only be demonstrated by appreciating variation in the quality of the offspring environment and life histories. Results are therefore consistent with egg size playing a significant role in shaping the phenotypic outcome of offspring in species that show even greater intra-specific variation in egg size than starlings.     

四川南充市郊区灰椋鸟生态的初步研究

2004年11月~2005年5月,在四川盆地中的南充市郊对灰椋鸟的生态进行了初步研究。于2004年11月10日首次观察到灰椋鸟,最后见到灰椋鸟的时间是2005年4月29日。白天,灰椋鸟多集成15~60只左右的群体活动;黄昏时分,在夜宿地往往集成大群(最大群体为410只左右),在南充市郊的种群密度为26.67只/km2。灰椋鸟现仅在市郊栖息,其栖息地划分为夜宿地、休息隐蔽地、取食地、饮水地。冬、春季灰椋鸟为杂食性鸟类,主要啄食蚯蚓、昆虫、植物叶和人类丢弃的食物。灰椋鸟的日活动活动节律有3个明显高峰,分别出现在晨昏和上午09∶00左右。讨论了灰椋鸟与农业生产的关系及城市光和噪声污染对灰椋鸟的影响。     

Polymorphism in plasma albumin of starlings (Sturnus vulgaris vulgaris L.) in Belgium

Polymorphism in plasma albumin (Alb.) is described in this paper. Albumin mobility was tested for polymorphism in 317 starlings by starch gel electrophoresis. Two phenotypes of albumin (AA = 92.42% and AB = 7.58%) were found. This system seems to be genetically controlled by two alleles, Alb^A (0.962) and Alb^B (0.038).     

Molecular analysis of a promiscuous, fluctuating mating system

The Soay sheep population of St. Kilda fluctuates widely in population size and sex ratio, so diat the level of male-male competition for mates varies from one rut to the next. In this paper we investigate variation in individual male breeding success in relation to age and population size at the rut, and its outcome in terms of lifetime breeding success. Since both sexes are promiscuous, and census-based behavioural data do not predict paternity, we conducted the whole analysis on breeding success derived by molecular techniques. We assumed that every male living in our study area during the rut (N= 68–294 in different years) was a candidate father for each subsequent lamb, and used the parentage inference software CERVUS 1.0, applied to up to 17 allozyme and microsatellite loci, to infer paternity at 95% and 80% confidence. Using 945 paternities assigned at 80% confidence, we show that juvenile rams (aged 7 months) and yearling rams (aged 19 months) regularly obtained paternities and that mean individual breeding success varied inversely with levels of competition in the rut for all age classes of ram. The proportion of young (juvenile and yearling) and adult rams gaining one or more paternities showed similar variation with population size, but the sibship size sired by young and adult breeders showed different patterns: adult rams sired larger sibships at low population size, while the size of sibships sired by young rams was small across all population sizes. Variable breeding success by young rams approximately halved the estimated coefficient of variation in lifetime breeding success of Soay rams.     

Seasonal variation in sex ratio and sexual egg dimorphism favouring daughters in first clutches of the spotless starling

We investigated possible pre‐hatching mechanisms of sex‐differential investment by females that may contribute to offspring sex‐ratio adjustment enhancing the fitness return from reproductive effort in the spotless starling (Sturnus unicolor). We found a seasonal shift in sex ratio from daughters to sons as the season advances. Furthermore, the probability of breeding at 1‐year old and recruitment into the breeding population in daughters is associated with laying date but not with mass at fledging. The reverse is true for males which rarely bred at 1‐year old. We also found that eggs containing female embryos are significantly heavier than those containing males in spite of the slight sexual dimorphism in favour of males. This suggests maternal control of provisioning, favouring daughters that may balance sibling mortality and competition with their brothers. Our results on seasonal variation in sex ratio and differential egg provisioning are consistent with an adaptive tactic in which mothers increase their reproductive return by enhancing the probability that daughters survive and breed in their first year of life.     

Thermal constraints on foraging in adult european starlings

Summary The operative temperature of the environment was estimated for starlings using hollow, unheated taxidermic mounts. On average, adults foraging in full sun were characterized by shorter foraging bouts than those adults foraging in full shade. Simultaneous observations of air temperature, operative temperature, and the foraging duration of adults indicated that air temperature was a poor predictor of the maximum length of a foraging bout. The operative temperature of the environment was not correlated to the maximum and mean length of foraging bouts for temperatures below 31.5°C, but was negatively related to maximum and mean foraging duration for values above 31.5°C. I also found that foraging adults experiencing high thermal loads (T _e31.5°C) were less likely to return to the nest with food. These results raise the possibility that adults may be limited in their utilization of foraging sites due to an inability to cope with heat load, and that much of the loafing behavior observed for breeding birds may be behavior to avoid heat stress. The implication for seasonal variation of clutch size is discussed.     

Allozyme polymorphism and interspecific relationships in the Common starling (Sturnus vulgaris) and Spotless starling (S. unicolor) (Aves: Sturnidae)

This paper reports a genetic study of Sturnus vulgaris and S. unicolor (Sturnidae), two similar bird species which have recently become sympatric in north-eastern Spain. Seven enzyme systems (alcohol dehydrogenase, esterase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, leucin aminopeptidase, L-lactate dehydrogenase and superoxide dismutase) were analyzed, resolving 22 presumed genetic loci with 28 alleles; 27 of them were found in both species. Gene flow was estimated to be number of migrants per generation (Nm) = 6, and genetic identities among populations were high, ranging from I = 0.96 to I = 0.99. On the whole, the results demonstrate that these Sturnus populations share a gene pool, showing slight genetic differences between the two starling speices.     

Does substrate quality influence take-off decisions in Common Starlings?

1. An instrumented perch was used to measure the reaction forces during take-off of starlings from perches of three thicknesses. There was no significant decrease in reaction force with decreasing perch thickness; however, over the range of perch sizes there was a 10-fold decrease in safety factor and a 400-fold increase in the energy of deflection of the thinnest perch.
2. The implications of these results are that birds do not change their take-off strategy when faced with perches of variable thickness and that, as a result, leaps from thin perches are very much less efficient than those from thicker perches. Birds appear not to adjust their leaping behaviour to minimize the risk of substrate failure during take-offs.