Winter Ecology And Conservation Strategy Of The Scaly-sided Merganser Mergus Squamatus

The scaly-sided merganser or Chinese merganser (Mergus squamatus) belongs toAnatidae of Anseriformes. It is a kind of special and rare birds in our country. It islisted in the first category of the nationally protected wildlife species in China and isregarded as an endangered species by IUCN in2002. Wintering areas include a widerange along the south of Yangtze River, where the Poyang Lake watershed in JiangxiProvince provides one of the main wintering habitats for this species in China. Thepopulation size of scaly-sided merganser is large and stable in Jiangxi. Currently,wintering scaly-sided mergansers are highly concerned by domestic and foreignscholars in Jiangxi. Previous studies of the behaviour, distribution and population sizeof this bird have been carried out in China, but only a little comprehensive research onwintering ecology and conservation strategy of this endangered species has beenpublished. To provide information for future conservation efforts, the author has donestudies from the perspectives of population size, distribution, group characteristics,habitat selection, behavior, home range, conservation threats and conservationstrategy of scaly-sided mergansers in eight sections of four rivers［Xiuhe Rriver, FuheRiver, Xinjiang River, Raohe River］of the Poyang Lake watershed, Jiangxi Provincefrom November2010to March2014. Results indicated that:Distribution and population dynamics: The least number of scaly-sidedmergansers in each month varied from93to114. This survey accounted for4.56%~11.40%of the total number of mergansers known existing globally. Preliminaryresults showed that, each river population was different in terms of time, also there isa big variation in different sections.The scaly-sided merganser wintering distributionis relatively narrow, but relatively fixed in different years. There are three sectionshaving large and stable population in the eight sections (Xiushui section, Yhuangsection, Yiyang and Wuyuan, respectively).Group characteristics: Groups of scaly-sided merganser were classified as male,female, mixed sex, solitary female and solitary male. During the wintering period, atotal of768mergansers belonging to145groups were observed. Of these groups,mixed sex groups were the most frequently encountered. Male and female solitarymergansers were also frequently encountered. There was temporal variation in grouptypes during the wintering period (P<0.01). With2~8individuals accounted for 80.69%of the total group number, indicating that mergansers preferred to select smallgroup sizes. The mean group size of mergansers was5.30±5.20individuals per groupduring the wintering period. The differences in frequency of different group typeswere significant. Group size varied with group type and may be related to localenvironment conditions such as digging sand, fishing and food availability. The sexratio is1.49. The differences in sex ratio of different month were significant. InNovember, the size of male mergansers was higher than that of other months and malemergansers solitary accounted for22.73%of the total group number. Whether it isrelated to the earlier arrival of male individuals in watering habitats needs to befurther confirmed needs to be further confirmed. Although the sex ratio weresignificant, most of the sex ratio between0.50~2.00in eight sections.Habitat selection: The main factors affecting the habitat selection of scaly-sidedmergansers in winter were water, foraging environment and human disturbance. Ofthe habitat factors, pH value, longitude, distance from the nearest shoal, and distancefrom the nearest avenue had greatest effects on habitat selection. The factors with theeigenvalues over0.6were compared among four major rivers by Kruskal-Wallis Tests.The results indicated that pH value, longitude and latitude were obviously differentfrom each other (P≤0.01), while the distance from nearest mining, distance fromnearest avenue, distance from nearest resident site showed statistical significance (P<0.05).Behavior：Feeding, resting, swimming and maintenance were the main winteringbehaviors of scaly-sided mergansers. Independent sample t-test was applied toanalyze the differences in behavior time budget between the male and the female.There was a significant difference in social behavior (P<0.05), other behaviors haveno significant difference (P>0.05). There may be two reasons:(1) Both male andfemale were mainly to gain energy with the same aim to survive during non-breedingperiod；(2) Male and female have similar body size. By one-way ANOVA analysis,feeding and resting behaviors of male and female occurred with obvious rhythm(P<0.05), the other behaviors occurred without obvious rhythm (P>0.05). Thetemperature has a great influence on Chinese Merganser wintering behavior. As to thetime budget, in <10°C month, feeding time was significantly shorter than that in>10°C month (P<0.05), however, swimming time was significantly longer (P>0.05). Thatis as the average temperature lower, the scaly-sided mergansers need more food intake.In order to supplement the energy consumption in cold weather, this bird reducedswimming behavior to decrease energy consumption. As to the daily behavioral rhythm, in>10°C month only vigilance behavior occurred with obvious rhythm(P<0.05), the other behaviors occurred without obvious rhythm (P>0.05). In>10°Cmonth feeding and resting behaviors occurred with obvious rhythm (P<0.05), theother behaviors occurred without obvious rhythm (P>0.05). The results indicated thatthe temperature could change the scaly-sided mergansers daily behavioral rhythm.Low temperature let the scaly-sided merganser depleted more energy at night,therefore the scaly-sided merganser spent more time on feeding to supplement energyin the morning. In>10°C month, there were two resting slight peaks in the noon andevening, however, in <10°C month resting kept high level from11:00to18:00(except13:00-13:59). The scaly-sided merganser adopted this strategy, becausein <10°C month there were low temperature in the afternoon and evening, the birdsincrease resting behaviors to decrease energy consumption from the afternoon. In thelow temperature conditions, the scaly-sided merganser increase the maintenance andresting behaviors. This result supports this view that birds in the low-temperatureenvironment will reduce activities to decrease energy consumption and heat loss.Daily range length and home range：The range length and home range of thescaly-sided mergansers were studied in Yihuang county of Jiangxi province. Resultsshow that the daily range length of scaly-sided merganser was3100±1313m, thedaily home range was122460±42019m2, the range of the whole wintering period was202350m2. There was no significant difference of the daily home range in differentmonths（F=0.658, P>0.05）. Significant differences of the daily home rang weredetected on January and February、February and March (P<0.05), but such differencewas not found in the daily range in other month（sP>0.05）. During the Spring Festivalin February, the more frequent human activities increased the scaly-sided merganser’sdaily home range. There was no significant correlation between the daily range lengthand the daily home range（R=0.256, n=12, P>0.05）. The daily range length have nosignificant correlation with length of sunshine, daily minimum and maximumtemperature and water level （P>0.05）. The daily home range have significantcorrelation with daily minimum temperature（R=0.817, df=7, P<0.01）, but not foundwith other factors. The range length and home range were slightly longer (or larger) inthe morning and afternoon, and shorter (or smaller) in the noon.Birds in the both sides and watercourse of the habitat river: A total of107species belonging to36families,13orders were recorded in the both sides andwatercourse of the scaly-sided merganser’s habitat river of Poyang Lake watershed.Of the107species, one species is listed in the first category of the nationally protected wildlife species in China and ten species are listed in the second category ofthe nationally protected wildlife species. Residents and winter migrants are the mostabundant species，which account for57.61%and35.51%of total species, respectively.In term of avifauna, Palaearctic elements, accounting for41.12%, are the mostcommon species, followed by Oriental elements (32.71%).Conservation threats and conservation strategy： Main threats to theconservation of the scaly-sided mergansers include sand mining, fishing, riparianvegetation and water pollution. We recommend the areas having scaly-sidedmergansers should be classified into the nearby protected area, and areas with largenumber of species can be set up as protection areas separately. The conservationstrategies are as follows:1) To strengthen river management;2) To constrain theinsensity of sand mining;3) To bring part of the areas into conservation areas;4) Toprohibit illegal fishing;5) To protect vegetation;6) To control water levelappropriately;7) To control water pollution.