Temporal increase in mtDNA diversity in a declining population

In small and declining populations levels of genetic variability are expected to be reduced due to effects of inbreeding and random genetic drift. As a result, both individual fitness and populations’ adaptability can be compromised, and the probability of extinction increased. Therefore, maintenance of genetic variability is a crucial goal in conservation biology. Here we show that although the level of genetic variability in mtDNA of the endangered Fennoscandian lesser white‐fronted goose Anser erythropus population is currently lower than in the neigbouring populations, it has increased six‐fold during the past 140 years despite the precipitously declining population. The explanation for increased genetic diversity in Fennoscandia appears to be recent spontaneous increase in male immigration rate equalling 0.56 per generation. This inference is supported by data on nuclear microsatellite markers, the latter of which show that the current and the historical Fennoscandian populations are significantly differentiated (F_ST = 0.046, P = 0) due to changes in allele frequencies. The effect of male‐mediated gene flow is potentially dichotomous. On the one hand it may rescue the Fennoscandian lesser white‐fronted goose from loss of genetic variability, but on the other hand, it eradicates the original genetic characteristics of this population.     

Serial agonistic attacks by greylag goose families, Anser anser, against the same opponent

It is known from primates that alliance partners may support each other's interests in competition with others, for example, through repeated agonistic attacks against a particular individual. We examined serial aggressive interactions between greylag goose families and other flock members. We found that repeated attacks towards the same individual were common and that up to five serial attacks by family members followed an initial attack. Family size did not affect the frequency of such serial attacks. Juvenile geese evidently benefited most from active social support through serial attacks. About 60% of the juveniles' lost primary interactions were subsequently reversed by another family member. This may be one of the reasons why juveniles rank higher in the social hierarchy than would be expected from their age and size alone. Losses in serial attacks predominantly occurred against other, presumably higher-ranking, family geese and ganders. We propose three major functions/consequences of serial attacks. Analogous to primates, serial attacks in greylag geese may serve to reinforce a losing experience of an opponent defeated in a preceding attack. On the side of the winning family, serial attacks may reinforce the experience of winning. Both winning and losing experiences are linked with physiological consequences in higher vertebrates, affecting the future social performance of winners or losers. Finally, serial attacks may signal the agonistic potential of a family to other flock members. This is supported by heart rate data, which indicate that greylags are competent to interpret third-party relationships.     

Where might the western Svalbard tundra be vulnerable to pink‐footed goose (Anser brachyrhynchus) population expansion? Clues from species distribution models

Pink-footed geese ( Anser brachyrhynchus ) breed in the Arctic, where their populations have doubled since the 1980s. There is concern that nesting geese disturb the fragile tundra and lead to a trophic cascade with strong top-down effects on vegetation and soil processes. A better understanding of the distribution of geese and factors that influence nest site selection is needed to highlight potential problem areas and assess the potential for further population expansion. To help infer the importance of environmental variables on nest site selection, we built generalized additive models using nest observations collected in 2003 and 2004 from the Sassendalen valley, Svalbard, along with a suite of geographical information system explanatory predictors. The fit of the models was very high (explaining over 72% of the deviance), and predictive power to independent samples indicated useful predictions that could discriminate between presences and absence of nests very well (area under the receiver operating characteristic curves exceeded 0.88). Significant predictors of nest site selection included elevation, slope, aspect, percentage of snow cover, percentage of foraging habitat cover, and a spatial autocovariate. Spatial predictions were applied to the broader Nordenskiöldsland region of Svalbard and highlighted the importance of previously unsurveyed locations for nesting.     

Condition Bias of Decoy-Harvested Light Geese During the Conservation Order

Evidence that decoy harvest techniques primarily remove individuals of poorer body condition is well established in short-lived duck species; however, there is limited support for condition bias in longer-lived waterfowl species, such as geese, where decoy harvest is considered primarily additive because of their high natural survival rates. We evaluated support for the harvest condition bias hypothesis of 2 long-lived waterfowl species, the lesser snow goose (Anser caerulescens caerulescens) and Ross's goose (Anser rossii). We used proximate analysis to quantify lipid and protein content of lesser snow and Ross's geese collected during the Light Goose Conservation Order (LGCO) in 2015 and 2016 during spring migration in Arkansas, Missouri, Nebraska, and South Dakota, USA. In each state, LGCO participants collected birds using traditional decoy techniques and we collected birds from the general population using jump-shooting tactics. Total body lipid content in both lesser snow and Ross's geese varied with age, region of harvest, and harvest type (decoy or jump-shooting). On average, adult lesser snow and Ross's geese harvested over decoys had 60 g and 41 g, respectively, fewer lipids than conspecifics collected using jump-shooting. We observed lower lipid reserves in decoy-shot geese in all 4 states sampled despite general gains in lipid reserves as migration chronology progressed. Our data support that the harvest condition bias extends to longer-lived waterfowl species and during a life-history event (spring migration) in which harvest is not normally observed. In the case of overabundant light geese, the disproportionate harvest of poorer-conditioned lesser snow and Ross's geese may serve as an additional challenge against any realized effects of harvest to reduce the population, in addition to extremely low harvest rates. © 2019 The Wildlife Society.     

The histological structure and histochemistry of the mucosa of the nasal conchae in geese,Anser anser

We investigated the histological structure and histochemistry of the nasal conchae of geese and compared these structures with those of other avian species. The rostral, middle and caudal conchae were dissected from the nasal cavity of eight geese, fixed in Carnoy’s solution and embedded in paraffin. The entrance of the rostral concha was lined by keratinized stratified squamous epithelium, which toward the middle concha was replaced by modified keratinized squamous epithelium, the deep layer of which opened into tubular glandular structures containing secretory epithelium on crypt-like invaginations. The lamina propria of the rostral concha contained numerous Grandry’s and Herbst corpuscles, which are pressure-sensitive receptors peculiar to waterfowl. The lamina propria of the middle concha contained solitary lymphoid follicles and lymphocyte infiltrations. The cartilaginous component of the middle concha was highly convoluted and resembled a spiral of two and a half scrolls, which were lined by pseudostratified columnar epithelium. We observed that unlike mammals, this epithelium contained mostly intraepithelial alveolar glands rather than goblet cells. The caudal concha was similar to the middle concha, but less convoluted. It was lined by olfactory epithelium and its lamina propria contained serous Bowman’s glands as well as olfactory nerve fibers. Histochemical examination demonstrated that while none of the conchae contained sulfated mucins, except for the cartilage, the intraepithelial glands of the rostral and middle conchae contained mostly carboxylated acidic mucin and some neutral mucin, and were thus of the mixed type. The outermost scroll of the spiral of the middle concha contained some periodate-Schiff stained mucins. Of the glands of the mucosa of the middle concha, the deep tubuloalveolar glands in the convex parts of the scrolls contained primarily acidic mucins, while the shallow intraepithelial alveolar glands in the concave parts of the scrolls contained primarily neutral mucins. Our findings indicate that the rostral and caudal conchae primarily have a sensory function and the middle concha participates in mucosal defense.     

Growth of Greater White-Fronted Goose Goslings Relates to Population Dynamics at Multiple Scales

The abundance of greater white-fronted geese (Anser albifrons frontalis) on the Arctic Coastal Plain (ACP) of northern Alaska, USA, has more than tripled since the late 1990s; however, recent rate of annual population growth has declined as population size increased, which may indicate white-fronted geese on the ACP are approaching carrying capacity. We examined rates of gosling growth in greater white-fronted geese at 3 sites on the ACP during 2012–2014 to assist with predictions of future population trends and assess evidence for density-dependent constraints on recruitment. We marked goslings at hatch with individually coded webtags and conducted brood drives during early August to capture, measure, and weigh goslings. Annual estimates of gosling mass at 32 days old (range = 1,190–1,685) indicate that goslings had obtained >60% of asymptotic size. This rate of growth corresponds with that of other goose species and populations with access to high-quality forage and no limitations on forage availability, and is consistent with the overall increase in abundance of white-fronted geese at the ACP scale. Contrary to most previous investigations, age-adjusted mass of goslings did not decline with hatch date. Goslings grew faster in coastal areas than at inland freshwater sites. Taken together, these findings suggest forage was not limiting gosling growth rates in either ecosystem, but forage was of greater quality in coastal areas where goose foraging habitat is expanding because of permafrost subsidence. Spatial patterns of gosling growth corresponded with local-scale patterns of population density and population change; the areas with greatest rates of gosling growth were those with the greatest population density and rates of population increase. We found little evidence to suggest forage during brood rearing was limiting population increase of white-fronted geese on the ACP. Factors responsible for the apparent slowing of ACP-wide population growth are likely those that occur in stages of the annual cycle outside of the breeding grounds. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.     

Effects of agricultural change on abundance, fitness components and distribution of two arctic-nesting goose populations

Intensification of agriculture since the 1950s has enhanced the availability, competitive ability, crude protein content, digestibility and extended growing seasons of forage grasses. Spilled cereal grain also provides a rich food source in autumn and in winter. Long‐distance migratory herbivorous geese have rapidly exploited these feeding opportunities and most species have shown expansions in range and population size in the last 50 years. Results of long‐term studies are presented from two Arctic‐breeding populations, the Svalbard pink‐footed goose and the Greenland white‐fronted goose (GWFG). GWFGs have shown major habitat shifts since the 1950s from winter use of plant storage organs in natural wetlands to feeding on intensively managed farmland. Declines in local density on, and abandonment of, unmodified traditional wintering habitat and increased reproductive success among those birds wintering on farmland suggest that density‐dependent processes were not the cause of the shift in this winter‐site‐faithful population. Based on enhanced nutrient and energy intake rates, we argue that observed shifts in both species from traditionally used natural habitats to intensively managed farmland on spring staging and wintering areas have not necessarily been the result of habitat destruction. Increased food intake rates and potential demographic benefits resulting from shifts to highly profitable foraging opportunities on increasingly intensively managed farmland, more likely explain increases in goose numbers in these populations. The geographically exploratory behaviour of subdominant individuals enables the discovery and exploitation of new winter feeding opportunities and hence range expansion. Recent destruction of traditional habitats and declines in farming at northern latitudes present fresh challenges to the well being of both populations. More urgently, Canada geese colonizing breeding and moulting habitats of white‐fronted geese in Greenland are further affecting their reproductive output.     

印度Ladakh地区斑头雁的数量、种群结构和栖息地利用

于 1998、 2 0 0 0和 2 0 0 2年在印度的Ladakh地区进行了野外考察以研究斑头雁的繁殖行为和种群大小。Ladakh地区的斑头雁集小群在淡水湖泊中的小岛上进行繁殖 ,不在树上和悬崖上繁殖。 5月份开始产卵。群内孵化的同步性较低。盐水湖岸上没有观察到进行繁殖或带有幼雏的斑头雁。作者所调查的Ladakh地区有 35 0 - 10 0 0只斑头雁 ,该物种的数量满足了Ramsar公约的有关规定 ,建议将该地区列为国际重要地区     

Ph?nologie und Raumnutzung von Bl?ssg?nsen (Anser albifrons) benachbarter Teilpopulationen am Unteren Niederrhein

Zusammenfassung Die vorliegende Untersuchung stellt Daten zur Phänologie und Raumnutzung der Blässgans in einem knapp 120 km² großen Untersuchungsgebiet am Unteren Niederrhein vor. Mooij (1993) unterschied im deutschen Teil der Überwinterungsregion fünf als Schlafkomplexe definierte Teilpopulationen. Diese nutzen Nahrungsräume über deren Überlappung noch keine Erkenntnisse vorliegen. Das Untersuchungsgebiet der vorliegenden Arbeit beinhaltet überwiegende Teile der linksrheinischen Nahrungsräume der beiden westlichsten dieser Teilpopulationen. Um die Überlappung der Nahrungsräume aufzuzeigen wird die Phänologie des Gesamtgebiets sowie getrennt für den Ost- und Westteil, den Nahrungsräumen der benachbarten Schlafkomplexe, beschrieben. Die ökologische Funktion des Rheinvor- und Hinterlandes, das sich im Anteil der nach NSG-Verordnung geschützten Bereiche stark unterscheidet, wurde ermittelt, indem die räumliche Verteilung der Gänse auf diese Bereiche für Sextadenintervalle bestimmt wurde. Der Beweidungsdruck auf das Vorland sowie das Nutzungsmuster ausgewählter Grünlandgebiete im Vorund Hinterland lieferte Informationen über den Einfluss abiotischer Faktoren auf die Nutzungsintensität und Tragkraft dieser Teilbereiche. Die Ergebnisse zeigen: (1) Die Gänsezahl stieg während der ersten Novemberhälfte auf ca. 20.000 an. Wintermaxima traten mit ca. 51.000 1997/98 und ca. 57.000 Individuen 1998/99 Ende Dezember auf. Im Spätwinter setzte abhängig von den Witterungsbedingungen allmählicher Abzug ein. (2) Fluktuationen der Bestandsgröße eines Nahrungsraums traten häufig mit entgegengesetzten Schwankungen im benachbarten Gebiet auf und können, wie im Einzelfall dokumentiert, mit einem Schlafplatzwechsel gekoppelt sein. (3) Die anteilige Nutzung des Rheinvorbzw. Hinterlandes lag 1997/98 bei ca. 42:58 und 1998/99 bei 27,5:72,5 Prozent. Im Jahresverlauf schwankte sie periodisch. (4) Die Gesamtbeweidung des Vorlandes war 1998/99 trotz größerer Population und längerer Rastperiode um 24 Prozent geringer als 1997/98. Dies lässt auf eine durch Temperatur- und Überschwemmungseinflüsse reduzierte Tragkraft schließen. (5) Ausgewählte Rheinvor- und Hinterlandgebiete kennzeichnet ein periodisches Nutzungsmuster. Dies wurde durch Hochwasser- und Temperaturverlauf wie folgt beeinflußt: Im Vorlandgebiet waren Besuchsfrequenz und mittlere Verbandsgröße im milden Winter 1997/98 besonders hoch, im strengen Winter 1996/97 und nach längerer Überflutung 1998/99 aber deutlich herabgesetzt. Im Hinterlandgebiet war die Besuchsfrequenz und mittlere Verbandsgröße im milden Winter 1997/98 am geringsten und 1998/99 bei ebenfalls relativ mildem Klima, aber durch Hochwassereinflüsse verminderter Tragkraft des Vorlandes, am höchsten. Der strenge Winter 1996/97 nahm eine Mittelstellung ein.

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Phenology and spatial distribution of White-fronted Geese (Anser albifrons) wintering in neighbouring roost sites on the Lower Rhine

Summary Based on frequent goose counts, data are presented on abundance and spatial distribution of White-fronted Geese wintering in the north-western part of the Lower Rhine area, North Rhine Westfalia, FRG, in an area of about 117 km². In accordance to the main roost sites in the lower Rhine valley, Mooij (1993) divided the wintering population into five subpopulations, called roost complexes, and put forward a definition of their foraging areas. No information on the degree of separation of these subpopulations or on overlapping of their foraging areas has so far been available. The study area of this investigation includes neighbouring foraging areas of the two western roost complexes in the German part of the Lower Rhine region. Based on frequent goose counting (two-days counts in 1997/98, almost daily counts in 1998/99) the abundance-phenology is described for the study area both as a whole and split up into eastern and western parts (B220-East, B220-west) corresponding to the two different roost-complexes. In this way it is possible to obtain informations on the overlap of foraging areas, which indicates regular goose movements between the subpopulations.To get information on the ecological function of mainly protected foreshore areas, defined as areas located riversides of the dike, and mainly unprotected polder areas outside of the dike, the spatial distributions of geese on these parts of the study area were determined for six-day intervals. The comparison of grazing activity on foreshore areas, counted almost daily in 1997/98 and 1998/99, afforded information about carrying capacity in relation to wintering conditions. In selected preferred foreshore and polder areas, counted almost daily since 1996/97, grazing patterns were used to analyze the impact of temperature and flooding periods on the carrying capacity and the spatial distribution of geese. Our data show: (1) Numbers of geese increased during the first half of November from a few hundred up to 20,000 birds. Winter maxima were reached in the last 10-day period of December with 51,000 birds in 1997/98 and 57,000 in 1998/99. The gradual departure of geese from the beginning of February depended on weather conditions. (2) The average number of geese was higher in the western part of the study area and the exploitation of the area started earlier than in the eastern part. (3) Fluctuations in goose numbers in both eastern or western parts of the study area were often related to complementary fluctuations in goose number in the neighbouring part of the study area, which is an indication of the overlap of the foraging areas. In one individual case it was possible, by following a great number of geese, to verify that complementary fluctuations could be connected with a change in roost sites. (4) The proportion of goose days spent on foreshore and polder areas was 42.4vs. 57.6% in 1997/98 and 27.5vs. 72.5% in 1998/99. (5) During the wintering periods the proportion of goose days showed periodical fluctuations, i.e., after a few days with large numbers of grazing geese on foreshore areas, there were weeks with very small goose numbers. (6) In spite of the larger population size and longer wintering period, in the colder winter with floodings of 1998/99 the absolute amount of grazing on foreshore areas was 24% less than in the warmer winter without floodings of 1997/98. This leads to the conclusion that the carrying capacity had been reduced by low temperature and flooding periods in 1998/99. (7) The grazing patterns in selected foreshore and polder pasture areas revealed the following information on foraging behaviour and the impact of abiotic factors on spatial distribution: (a) both selected pasture areas were characterized by periodical grazing patterns. (b) in the foreshore area goose frequency and average flock size was highest in the mild winter 1997/98 while in the severe winter 1996/97 and after the longer flooding period in the early winter of 1998/99, goose frequency and average flock size was distinctly reduced. (c) in contrast, goose-frequency and average flock size in the polder area was lowest in 1997/98 and highest during the colder weather conditions in 1998/99 when a reduced carrying capacity by flooding was evident in the foreshore area. The severe winter 1996/97 was characterized by intensive grazing, especially after the frost period.