Experimental refuges for migratory waterfowl in Danish wetlands. I. Baseline assessment of the disturbance effects of recreational activities

1. Potential human sources of disturbance, including fishing, sailing, windsurfing and different types of waterfowl hunting, are described and their effects on autumn-staging waterbirds, including mute swan, wigeon and coot, were examined at a coastal wetland in Denmark from 1985 to 1988.
2. Bird and human distributions were superimposed on the distribution of submerged vegetation and water depths to identify the extent of spatial overlap; likewise, seasonal and diurnal temporal overlap in bird abundance, and human activities were defined. Behavioural and distributional reactions of waterbirds to different human activities, in terms of escape distances, disruption of activity patterns and redistribution, were assessed to establish their relative effects.
3. Sailing and windsurfing showed little spatial overlap, and fishing partial spatial overlap with bird distributions; these activities almost ceased before the peak in autumn bird numbers. Hunting showed a high degree of spatial and temporal overlap with bird presence.
4. Birds responded to windsurfing at greatest distances, whereas hunting (especially from mobile punts) caused the longest disruptions to activities of waterfowl. In terms of behaviour and redistribution, wigeon was more affected by shooting than was mute swan or coot. One or two mobile shooting punts reduced wigeon numbers, whereas numbers were unaffected by the presence of up to 4–6 stationary punts; fishing boats had no effect on wigeon abundance.
5. Hunting, especially shooting from mobile punts, was identified as the most disturbing human activity in relation to staging waterfowl in this area. Similar results and conclusions were reached in another comparable study area. The results have implications for refuge designs and zoning of disturbing recreational activities.     

Chewing Lice of Swan Geese (Anser cygnoides): New Host-Parasite Associations

Chewing lice (Phthiraptera) that parasitize the globally threatened swan goose Anser cygnoides have been long recognized since the early 19th century, but those records were probably biased towards sampling of captive or domestic geese due to the small population size and limited distribution of its wild hosts. To better understand the lice species parasitizing swan geese that are endemic to East Asia, we collected chewing lice from 14 wild geese caught at 3 lakes in northeastern Mongolia. The lice were morphologically identified as 16 Trinoton anserinum (Fabricius, 1805), 11 Ornithobius domesticus Arnold, 2005, and 1 Anaticola anseris (Linnaeus, 1758). These species are known from other geese and swans, but all of them were new to the swan goose. This result also indicates no overlap in lice species between older records and our findings from wild birds. Thus, ectoparasites collected from domestic or captive animals may provide biased information on the occurrence, prevalence, host selection, and host-ectoparasite interactions from those on wild hosts.     

Artificial incubation of trumpeter swan eggs: Selected factors affecting hatchability

Eggs collected from captive trumpeter swans (Cygnus buccinator) in 1993 (n = 33) and 1994 (n = 42) were artificially incubated with careful monitoring to identify factors contributing to the low hatch success reported by the Ontario Trumpeter Swan Restoration Program. Fertility was > 80% in both years, whereas hatch success of fertile eggs was 14.3% (n = 4) of 28 eggs in 1993 and 37.1% (n = 13) of 35 eggs in 1994. Necropsy of non‐viable eggs indicated a high incidence of embryonic mortality during early and late incubation. Early embryonic mortality was associated with egg storage times exceeding 7 days (P < 0.05) and bacterial contamination of eggs (P < 0.01). Late mortality was associated with (P < 0.001) increased weight loss during incubation period and may have resulted from incubator temperature and humidity fluctuations. We established patterns of weight loss for eggs and determined that hatched eggs lost 11–15% of initial mass and that weight loss >15% resulted in embryo mortality. Results from this study indicate that collection and handling of eggs before incubation and precise control of the incubator environment are critical to hatchability of eggs. Zoo Biol 18:403–414, 1999. © 1999 Wiley‐Liss, Inc.     

Mute swan (Cygnus olor) winter distribution and numerical trends over a 16-year period (1987/1988–2002/2003) in France

The numbers of mute swans (Cygnus olor) at 98 wetland locations in France were monitored monthly during the winter (December–February) for 16 years by a national network of observers as part of a broader national wildfowl monitoring scheme. Log-linear Poisson regressions with TRIM software were used to estimate missing counts and produce national numbers and indices. These corrected indices were in turn used to calculate an average annual rate of change and the associated confidence interval that subsequently enabled the computation of a cumulated (global) rate of change and associated confidence interval. The latter were interpreted to classify the numerical trends over the whole period. For the six wetlands with the largest numbers of mute swans, average numbers of swans were also compared between wetlands and months. General Linear Models were then used to test simultaneously for (1) differences between years and between wetlands for each month and (2) between years and between months separately for each of the six wetlands. The mute swan average annual rate of change was >7% for each month. The global rate of variation corresponded to a “strong increase” after TRIM analyses. This result strongly supports the necessity of maintaining both national and international monitoring schemes in order to be able to quickly detect major increases in swan numbers at specific sites, particularly where increasing numbers may result in a conflict with farmers or in inter-specific competition with other waterbirds and/or represent a possible sanitary/public health hazard due to the potential for swans to carry avian influenza viruses.     

环境温度对大天鹅越冬行为和活动区的影响

环境温度变化通过影响鸟类的行为进而使其活动区也发生变化,探讨三者之间的关联性有助于理解鸟类是如何通过行为调整以适应周围环境的变化,来满足自身的生理需求。本研究通过卫星跟踪的方法获得了在河南三门峡湿地越冬的31只大天鹅(Cygnus cygnus)详细位点数据,在ArcGIS和R语言中采用核密度估计法计算大天鹅的活动区面积,在SPSS中采用Spearman分析平均温度与活动区面积的相关性;并利用瞬时扫描法获得大天鹅越冬行为观察数据,采用非参数Kruskal Wallis检验对大天鹅行为的差异性进行分析,探讨了环境温度与大天鹅越冬行为和活动区三者之间相互作用的模式。研究表明,从越冬初期至后期,随着环境温度的先下降后升高,大天鹅的取食、运动、静息等主要行为发生了较大的变化,静息和取食行为先增加后减少,运动行为则先减少后增加。越冬不同时期的核心区和活动区面积与温度呈显著性正相关。大天鹅在不同时段的活动区面积大小整体上均呈现出先减少后增加的趋势。随着环境温度的变化,大天鹅的越冬行为也随之发生了调整,进而使活动区面积发生改变,主要体现在越冬初期大天鹅通过增加活动区面积及时补充能量增加体能,越冬中期减少活动保持能量需求,越冬后期增加盘旋飞行使得活动区面积增大等。大天鹅这一系列行为和活动区的调整都是为了更好地满足越冬不同时期的生理需求。     

Influence of migrant tundra swans (Cygnus columbianus) and Canada geese (Branta canadensis) on aquatic vegetation at Long Point, Lake Erie, Ontario

Numerous studies have shown that large, herbivorous waterfowl can reduce quantity of aquatic plants during the breeding or wintering season, but relatively few document herbivory effects at staging areas. This study was done to determine if feeding activities of tundra swans (Cygnus columbianus columbianus) and Canada geese (Branta canadensis) had a measurable additive influence on the amount of aquatic plants, primarily muskgrass (Chara vulgaris), wild celery (Vallisneria americana), and sago pondweed (Potamogeton pectinatus), removed during the fall migration period at Long Point, Lake Erie, Ontario. Exclosure experiments done in fall 1998 and 1999 showed that, as compared to ducks and abiotic factors, these two large herbivorous waterfowl did not have any additional impact on above or below ground biomass of those aquatic plants. As expected, however, there were substantial seasonal reductions in above-ground and below-ground biomass of aquatic plants in wetlands that were heavily used by all waterfowl. We suggest that differences in large- and small-scale habitat use, feeding activity, and food preferences between tundra swans and other smaller waterfowl as well as compensatory herbivory contributed to our main finding that large waterfowl did not increase fall reductions of Chara spp, V. Americana, and P. pectinatus biomass.     

Characterization of microsatellite loci isolated in trumpeter swan (Cygnus buccinator)

Primers for 16 microsatellite loci were developed for the trumpeter swan (Cygnus buccinator), a species recovering from a recent population bottleneck. In a screen of 158 individuals, the 16 loci were found to have levels of variability ranging from two to seven alleles. No loci were found to be linked, although two loci repeatedly revealed significant departures from Hardy–Weinberg equilibrium. Amplification in the closely related tundra swan (Cygnus columbianus) was successful for all except one locus. These microsatellite loci will be applicable for population genetic analyses and ultimately aid in management efforts.     

大天鹅肾组织显微结构及细胞凋亡相关蛋白的表达

为了解大天鹅(Cygnus cygnus)肾的结构特点和相关活性蛋白的表达情况,采用石蜡切片、H.E染色和免疫组化法,观察分析大天鹅的肾组织显微结构和Caspase-3、Bcl-2、Bax及AQP-3的表达。大天鹅的肾组织主要由肾单位、集合管和结缔组织构成;肾小球由一团盘曲的毛细血管构成,近端小管由单层立方上皮组成,游离面有刷状缘,细段由单层扁平上皮组成,远端小管由立方形上皮组成,腔面无刷状缘。近端小管上皮细胞中有Caspase-3、Bcl-2、Bax阳性表达,远端小管上皮细胞有Caspase-3阳性表达,集合管上皮细胞有Bcl-2、AQP-3阳性表达,在肾小球毛细血管内皮有Bcl-2阳性表达。Caspase-3、Bcl-2、Bax及AQP-3共同调节细胞的生长与凋亡过程,可能在稳定鸟类肾单位和集合管结构及调节肾组织水平衡等方面有重要的作用。     

新疆巴音布鲁克繁殖期大天鹅的生境选择

2011年和2012年的6-8月,考察了分布于巴音布鲁克自然保护区的大天鹅(Cygnus cygnus)种群,分析了大天鹅巢址选择特征和育雏期生境选择特征。在野外共记录到了26个大天鹅巢址。与对照样方比较发现,植被高度、水深、所在水域面积、距干扰源距离和安全等级存在显著差异。进一步逻辑斯蒂回归分析表明,植被高度、水深和安全等级是影响大天鹅巢址选择的最主要的3种生境因子。采用样线法对育雏期大天鹅的生境选择进行了调查,发现大天鹅对沼泽湿地表现出正选择性,对草地表现出负选择性。样方法调查中,利用样方与对照样方比较发现,9种生境因子均存在显著差异,逻辑斯蒂回归分析表明,距干扰源距离和安全等级是影响大天鹅育雏期生境选择的最重要的两种因子。这样的选择机制有利于大天鹅更好的躲避敌害,顺利完成孵化和育雏工作。     

Mute Swans’ Impact on Submerged Aquatic Vegetation in Chesapeake Bay

Abstract: Mute swans (Cygnus olor) are poorly studied despite their potential to impact submerged aquatic vegetation (SAV). We measured vegetation characteristics (i.e., percent cover, shoot density, and canopy ht) of SAV beds in controls (unfenced), 2-year exclosures, and 1-year exclosures at 18 sites in the Chesapeake Bay, Maryland, USA, to quantify the impact of herbivory by mute swans on SAV during 2003 and 2004. Mute swan herbivory had a substantial adverse impact on percent cover, shoot density, and canopy height of SAV. At the end of the study mean percent cover, shoot density, and canopy height in the controls were lower by 79%, 76%, and 40%, respectively, as compared to those in 2-year exclosures. During 2004, percent cover, shoot density, and canopy height increased by 26%, 15%, and 22%, respectively, between early and late seasons of SAV growth in exclosures, but they decreased by 36%, 41%, and 18%, respectively, in the controls. Paired mute swans predominantly occupied 6 of 7 moderate-depth sites (0.76-0.99 m), and these sites experienced less (i.e., 32-75%) SAV reduction. All (n = 7) shallow water sites (0.50-0.75 m) were predominantly occupied by mute swan flocks, and percent cover reduction of SAV was as high as 75-100% at these sites. Mute swan flocks also predominantly occupied 3 of the 5 deep-water sites (≥1 m) and 1 of 7 moderate-depth sites, wherein we recorded considerable (i.e., 77-93%) SAV reduction. Thus, considering that flocks are more detrimental to SAV as compared to paired mute swans, we recommend that initial emphasis primarily be placed on controlling mute swans in flocks and secondarily on pairs.