Age effects on clutch size and laying dates of individual female Lesser Snow Geese Anser caerulescens

It is well known in many species of birds that mean clutch size increases and laying date advances with increasing age of the female. This has been interpreted widely as being due to some maturation process in which the performance of individual birds improves as they age. There are two alternative explanations, however. Birds which lay small clutches and lay late may have a higher mortality and be under-represented in the later year samples, or birds with a propensity to lay large and early clutches may enter the breeding population at a later age. In an attempt to discriminate between these alternatives, the reproductive performances of individual Snow Geese were examined over a series of years. Clutch size increased and laying date advanced for these individuals as it did for the population as a whole, thus confirming the maturation hypothesis.     

Is there a trade-off between egg weight and clutch size in wild Lesser Snow Geese (Anser c. caerulescens)?

Previous studies of arctic nesting geese suggest that laying is limited by the size of a female's body reserves and that larger eggs contain more nutrients. These observations imply a life-history trade-off between egg size and clutch size which may give rise to a negative genetic correlation between the two characters. We estimated the genetic correlation between egg weight and clutch size using measurements from mothers and their daughters in a wild population of Lesser Snow Geese Anser caerulescens caerulescens. Between 65 and 80 % of the variance in egg weight is attributable to differences between individuals, and heritability of egg weight is about 60 %. In contrast, 10–20 % of the variance in clutch size is attributable to differences between individuals, and heritability of clutch size is about 15 %. The genetic correlation coefficient between egg weight and clutch size ranges from 0.09 to 0.32 and does not differ significantly from zero. We discuss the possible reasons for the lack of the expected negative genetic correlation.     

Time budgets of Snow Geese Chen caerulescens and Ross's Geese Chen rossii in mixed flocks: implications of body size, ambient temperature and family associations

Body size affects foraging and forage intake rates directly via energetic processes and indirectly through interactions with social status and social behaviour. Ambient temperature has a relatively greater effect on the energetics of smaller species, which also generally are more vulnerable to predator attacks than are larger species. We examined variability in an index of intake rates and an index of alertness in Lesser Snow Geese Chen caerulescens caerulescens and Ross's Geese Chen rossii wintering in southwest Louisiana. Specifically we examined variation in these response variables that could be attributed to species, age, family size and ambient temperature. We hypothesized that the smaller Ross's Geese would spend relatively more time feeding, exhibit relatively higher peck rates, spend more time alert or raise their heads up from feeding more frequently, and would respond to declining temperatures by increasing their proportion of time spent feeding. As predicted, we found that Ross's Geese spent more time feeding than did Snow Geese and had slightly higher peck rates than Snow Geese in one of two winters. Ross's Geese spent more time alert than did Snow Geese in one winter, but alert rates differed by family size, independent of species, in contrast to our prediction. In one winter, time spent foraging and walking was inversely related to average daily temperature, but both varied independently of species. Effects of age and family size on time budgets were generally independent of species and in accordance with previous studies. We conclude that body size is a key variable influencing time spent feeding in Ross's Geese, which may require a high time spent feeding at the expense of other activities.     

Intra-seasonal decline of clutch size in Lesser Snow Geese

Summary Different mechanisms proposed to explain the intra-seasonal decline in clutch size of Lesser Snow Geese (Anser caerulescens caerulescens) were tested at the La Perouse Bay colony, Manitoba, Canada. Ovary examination of females collected after laying revealed that the actual number of eggs produced per female decreased over the laying period. This finding eliminates nest-parasitism, partial clutch predation and renesting attempts as sufficient explanations for seasonal clutch size decline. Follicular atresia induced by reserve depletion was also rejected since its occurrence was similar among early and late nesters. The decline in clutch size was observed within age-classes, and therefore age effects on clutch size and laying date per se do not account for the observed relationship. Clutch size and laying date were respectively positively and negatively correlated with the amount of nutrient reserves in females at the onset of laying, and also covaried within individuals observed breeding in several seasons. Laying date repeatability was estimated at 0.22. It is postulated that the seasonal decline in clutch size results mainly from a positive feed-back of female's nutrient reserves on the hormones controlling ovary development. Hatching synchrony or shortness of the breeding season may be the ultimate factors responsible for the intra-seasonal clutch size decline in Lesser Snow Geese.     

Foraging time and dietary intake by breeding Ross's and Lesser Snow Geese

We compared foraging times of female Ross's (Chen rossii) and Lesser Snow Geese (Chen caerulescens caerulescens) breeding at Karrak Lake, NT, Canada and examined variation due to time of day and reproductive stage. We subsequently collected female geese that had foraged for known duration and we estimated mass of foods consumed during foraging bouts. Female Ross's Geese spent more time foraging (mean % - SE =28.4ǃ.3%; P=0.0002), on average, than did female Lesser Snow Geese (21.5 - 1.4%). Foraging time by female geese differed among reproductive stages, but differences were not consistent among time periods (stage-by-time block interaction, P=0.0003). Females spent considerably more time foraging during prelaying and laying than during incubation. Ross's Geese also spent a greater percent of time feeding (83.0DŽ.8%) during incubation recesses than did Lesser Snow Geese (60.9Dž.6%). Consumption of organic matter during foraging bouts was minimal; estimated consumption averaged 9.6dž.0 and 12.4dž.6 g (mean - SE) dry mass/day before incubation and 5.9DŽ.0 and 5.7DŽ.1 g dry mass/day during incubation for Lesser Snow and Ross's Geese, respectively. Diets consisted primarily of mosses (bryophytes), Chickweed (Stellaria spp.) and Sedges (Carex spp.). Before incubation, eggshell consumption was estimated as 4.3Dž.2 and 0.4ǂ.3 g dry mass/day for Lesser Snow and Ross's Geese, respectively; neither species consumed eggshell during incubation. We conclude that eggshell from nests of previous years is likely an important source of dietary calcium used to meet mineral demands of eggshell formation at Karrak Lake. Our findings of wide disparities between foraging time and food intake indicate that results from studies that do not directly measure intake rates remain equivocal. Finally, we propose four hypotheses accounting for foraging effort that evidently yields little nutritional or energetic benefit to geese nesting at Karrak Lake.     

Distribution and Habitat Use of Ross's and Lesser Snow Geese During Late Brood Rearing

ABSTRACT We assessed spatial distribution and habitat use by Ross's and lesser snow geese (Chen rossii and C. caerulescens caerulescens) during late brood rearing to begin understanding goose-habitat interactions and monitoring key habitats around a rapidly growing nesting colony located at Karrak Lake, Nunavut, Canada. We conducted aerial surveys to count geese and georeference locations, then used Landsat Thematic Mapper satellite imagery to identify habitats associated with each flock. We observed 435 and 407 flocks and 36,287 and 32,745 birds in 1994 and 1995, respectively. Birds were somewhat uniformly distributed over the 5,000-km² study area, with larger aggregations occurring closer to the coast, about 70 km from the colony. We assessed habitat use using Bonferroni intervals at both the flock and individual scales. At the flock level, birds avoided lichen-heath, used other terrestrial habitats as available, and selected freshwater. At the individual level, geese selected lowland habitats: wet sedge meadow, hummock graminoid tundra, and freshwater, which accounted for about 70% of the birds observed, and avoided upland habitats. Selection of lowland habitats is likely due to greater availability of food and easier predator avoidance compared to drier upland areas. Because most geese in our study used freshwater habitats, our results demonstrate that assessment of carrying capacity, at least in the central Arctic, must be expanded beyond the coastal salt marshes traditionally considered by researchers and managers as primary brood-rearing habitat for mid-continent light geese.     

Genetic modelling: an analysis of a colour polymorphism in the Snow Goose (Anser caerulescens)

Previous studies of colour polymorphism in the Snow Goose [ Anser caerulescens ; failed to consider and reject alternative hypotheses to that of a single locus with incomplete dominance. Utilizing data from a long-term study of a wild population, we test the validity of these earlier results by considering two alternatives: (1) a single locus with multiple allelism and (2) a threshold polygenic system. Our analyses corroborate the original model, but emphasize the importance of testing all plausible hypotheses.     

Changes in Agriculture and Abundance of Snow Geese Affect Carrying Capacity of Sandhill Cranes in Nebraska

ABSTRACT The central Platte River valley (CPRV) in Nebraska, USA, is a key spring-staging area for approximately 80% of the midcontinent population of sandhill cranes (Grus canadensis; hereafter cranes). Evidence that staging cranes acquired less lipid reserves during the 1990s compared to the late 1970s and increases in use of the CPRV by snow geese (Chen caerulescens) prompted us to investigate availability of waste corn and quantify spatial and temporal patterns of crane and waterfowl use of the region. We developed a predictive model to assess impacts of changes in availability of corn and snow goose abundance under past, present, and potential future conditions. Over a hypothetical 60-day staging period, predicted energy demand of cranes and waterfowl increased 87% between the late 1970s and 1998–2007, primarily because peak abundances of snow geese increased by 650,000 and cranes by 110,000. Compared to spring 1979, corn available when cranes arrived was 20% less in 1998 and 68% less in 1999; consequently, the area of cornfields required to meet crane needs increased from 14,464 ha in 1979 to 32,751 ha in 1998 and 90,559 ha in 1999. Using a pooled estimate of 88 kg/ha from springs 1998–1999 and 2005–2007, the area of cornfields needed to supply food requirements of cranes and waterfowl increased to 65,587 ha and was greatest in the eastern region of the CPRV, where an estimated 54% of cranes, 47% of Canada geese (Branta canadensis), 45% of greater white-fronted geese (Anser albifrons), and 46% of snow geese occurred during ground surveys. We estimated that a future reduction of 25% in available corn or cornfields would increase daily foraging flight distances of cranes by 27–38%. Crane use and ability of cranes to store lipid reserves in the CPRV could be reduced substantially if flight distance required to locate adequate corn exceeded a physiological maximum distance cranes could fly in search of food. Options to increase carrying capacity for cranes include increasing accessibility of cornfields by restoring degraded river channels to disperse roosting cranes and increasing wetland availability in the Rainwater Basin to attract snow geese using the CPRV.     

The Lesser Snow Goose on Wrangel Island: Trophic Interactions with Ruminants and Breeding Habitat Selection

The lesser snow goose (Anser caerulescens caerulescens) has been exterminated across a vast area of Eurasia. At present, it is unable to regenerate there, though its population in North America has reached fifteen million. In Eurasia, the only major nesting colony still persists on Wrangel Island, where the geese use the trophic resources together with ruminants. An assessment of the competitive networks and the trophic interactions between the geese and the ruminants was performed. The analysis of the significance of the trophic niche overlap and the competitive advantages of geese in the habitat preferences has proved that the ruminants are stronger competitors for trophic resources than the geese. It has been ascertained that the levels of competition for trophic resources and/or resource shortages are higher across the habitats of most types associated with the goose colony. The level of the competition for trophic resources is lower, and the feed resources are more diverse and abundant in the habitats that are used by the geese after leaving the colony. It can be concluded that the shortage of resources and/or the stronger competitors for trophic resources (the ruminants) cannot prevent restoration of extinct colonies or the formation of new colonies with a recent increase in the size of the goose population on Wrangel Island. The distribution, abundance, and quality of trophic resources and the competition for them with ruminants do not determine the goose choice of a habitat for a nesting colony. The choice depends on the microclimate and, probably, on a range of other factors.     

Explaining co-occurrence among helminth species of lesser snow geese (Chen caerulescens) during their winter and spring migration

The digestive tracts of 771 lesser snow geese (Chen caerulescens) collected from January to May 1983 from 12 locations (27 samples) were examined for helminth parasites to determine whether parasite species present in wintering geese or in spring migrants occurred independently of each other. Nine helminth species were identified. Seven had mean prevalences >5% and were the focus of this study. Six of those species were waterfowl generalists, one was a goose specialist. Our primary objective was to assess the potential contribution of factors, other than species interactions, in determining patterns of co-occurrence between helminth species. There were few negative relationships between helminth species, regardless of whether presence-absence or abundance data were used. However, some species pairs showed recurrent and significant co-occurrences. There were similar and significant effects of timing of sampling, host gender, and host age, on prevalence and mean abundance of particular species. Co-occurrences were found for those species that showed seasonal declines in prevalence, for those expected to have high colonizing ability based on host age profiles (using abundance data), and for abundant species that may have shared vectors or environmental conditions favorable for transmission. Thus, similarities between parasites in their abundance, transmission biology, and phenology seem sufficient to explain species co-occurrences without invoking other processes such as species interactions. Received: 18 March 1996 / Accepted: 20 April 1999     

Identification of restriction-fragment-length polymorphisms in genomic DNA of the lesser snow goose (Anser caerulescens caerulescens)

A genomic library of partially EcoRI-digested DNA from the lesser snow goose, Anser caerulescens caerulescens, was constructed in the phage vector Charon 4. Phage containing only unique sequences were identified by screening plaques with 32P-labeled genomic DNA. Restriction-fragment- length polymorphisms (RFLPs) were identified by probing DNA from 11-13 male birds from the breeding colony at La Perouse Bay. Of the 17 probes examined, all detected RFLPs with at least one of EcoRi, HindIII, Msp1, and Taq1. Several of them identified highly variable regions with multiple alleles. These RFLPs are valuable DNA markers that can be used for (1) the examination of DNA variation, relatedness, and genetic distance and (2) assessing paternity and maternity. These data suggest that there are higher levels of variation of DNA sequence in birds than had previously been thought to exist.      

笼养暗腹雪鸡的繁殖

报道了暗腹雪鸡在笼养条件下的配对、领域、求偶行为、巢和卵、卵的受精率及人工孵化等情况。     

陕西红碱淖白喉林莺繁殖生态

2012~2013年每年的4~7月,在陕西神木县红碱淖(39°04'21″~39°04'43″N,109°53'12″~109°53'40″E)对白喉林莺(Sylvia curruca)的繁殖生态进行了研究。结果表明,白喉林莺4月末迁来繁殖,5月初开始营巢于油蒿(Artemisia ordosia)、臭柏(Sabina vulgaris)和沙棘(Hippophae rhamnoides)灌丛中,巢口向上呈深杯状,巢由柳絮、枯枝和干草编织而成。对33个巢的参数进行了测量,巢外径(9.62±0.227)cm,巢内径(5.21±0.084)cm,巢深(5.05±0.160)cm,巢高(9.03±0.185)cm,巢距地面高度(24.91±1.084)cm,巢约位于植株高度的1/3处(由下而上)。营巢成功率为77.1%(n=35),窝卵数4~5枚(n=27),卵重(7.49±0.021)g,卵长径(17.27±0.057)mm,卵短径(12.86±0.080)mm(n=130)。孵化期为11~13 d,孵化率为93.1%,雏鸟出飞为90.9%。雏鸟的形态参数生长符合Logistic曲线方程拟合。植被高度、植被盖度和单株植物冠径是制约白喉林莺巢址选择的主要因素,同时恶劣天气和人为干扰是影响繁殖成效的主要原因。     

Seasonal changes in plasma prolactin concentration and carcass lipid levels in the lesser snow goose (Anser caerulescens caerulescens)

• 1.1. Plasma prolactin levels did not differ significantly between groups of birds collected at different times during the first year of life.
• 2.2. In adult males and females, highest plasma prolactin concentrations were evident in June (20.7 ± 7.8 and 20.4 ± 4.4 ng/ml respectively), probably associated with the incubation of eggs and rearing of young in the nest, whereas plasma prolactin levels in adult males and females collected at other times of the year were relatively stable and did not differ significantly between groups.
• 3.3. With the exception of the adults sampled in June, the prolactin levels in the adults were in the same range as those in the embryo gosling and yearling Snow Geese.
• 4.4. The concentrations of fat in both mature and immature birds was not related to the plasma prolactin concentration; maximal concentrations of carcass fat were observed during the northerly migration whereas maximum concentrations of prolactin were observed at the end of incubation when fat deposits were depleted.

     

Nitrate nutrition enhances zinc hyperaccumulation in Noccaea caerulescens (Prayon)

Nitrate fertilization has been shown to increase Zn hyperaccumulation by Noccaea caerulescens (Prayon) (formerly Thlaspi caerulescens). However, it is unknown whether this increased hyperaccumulation is a direct result of NO₃ ^? nutrition or due to changes in rhizosphere pH as a result of NO₃ ^? uptake. This paper investigated the mechanism of NO₃ ^?-enhanced Zn hyperaccumulation in N. caerulescens by assessing the response of Zn uptake to N form and solution pH. Plants were grown in nutrient solution with 300 μM Zn and supplied with either (NH₄)₂SO₄, NH₄NO₃ or Ca(NO₃)₂. The solutions were buffered at either pH 4.5 or 6.5. The Zn concentration and content were much higher in shoots of NO₃ ^?-fed plants than in NH₄ ⁺-fed plants at pH 4.5 and 6.5. The Zn concentration in the shoots was mainly enhanced by NO₃ ^?, whereas the Zn concentration in the roots was mainly enhanced by pH 6.5. Nitrate increased Zn uptake in the roots at pH 6.5 and increased apoplastic Zn at pH 4.5. Zinc and Ca co-increased and was found co-localized in leaf cells of NO₃ ^?-fed plants. We conclude that NO₃ ^? directly enhanced Zn uptake and translocation from roots to shoots in N. caerulescens.     

Winter Fidelity and Apparent Survival of Lesser Snow Goose Populations in the Pacific Flyway

Abstract The Beringia region of the Arctic contains 2 colonies of lesser snow geese (Chen caerulescens caerulescens) breeding on Wrangel Island, Russia, and Banks Island, Canada, and wintering in North America. The Wrangel Island population is composed of 2 subpopulations from a sympatric breeding colony but separate wintering areas, whereas the Banks Island population shares a sympatric wintering area in California, USA, with one of the Wrangel Island subpopulations. The Wrangel Island colony represents the last major snow goose population in Russia and has fluctuated considerably since 1970, whereas the Banks Island population has more than doubled. The reasons for these changes are unclear, but hypotheses include independent population demographics (survival and recruitment) and immigration and emigration among breeding or wintering populations. These demographic and movement patterns have important ecological and management implications for understanding goose population structure, harvest of admixed populations, and gene flow among populations with separate breeding or wintering areas. From 1993 to 1996, we neckbanded molting birds at their breeding colonies and resighted birds on the wintering grounds. We used multistate mark-recapture models to evaluate apparent survival rates, resighting rates, winter fidelity, and potential exchange among these populations. We also compared the utility of face stain in Wrangel Island breeding geese as a predictor of their wintering area. Our results showed similar apparent survival rates between subpopulations of Wrangel Island snow geese and lower apparent survival, but higher emigration, for the Banks Island birds. Males had lower apparent survival than females, most likely due to differences in neckband loss. Transition between wintering areas was low (<3%), with equal movement between northern and southern wintering areas for Wrangel Island birds and little evidence of exchange between the Banks and northern Wrangel Island populations. Face staining was an unreliable indicator of wintering area. Our findings suggest that northern and southern Wrangel Island subpopulations should be considered a metapopulation in better understanding and managing Pacific Flyway lesser snow geese. Yet the absence of a strong population connection between Banks Island and Wrangel Island geese suggests that these breeding colonies can be managed as separate but overlapping populations. Additionally, winter population fidelity may be more important in lesser snow geese than in other species, and both breeding and wintering areas are important components of population management for sympatric wintering populations.