Effects of intra- and interspecific brood parasitism on a precocial host, the canvasback, Aythya valisineria

Canvasback ducks (Aythya valisineria) suffer both intra- andinterspecific brood parasitism. During 3 years in Manitoba,80% of canvasback nests (n = 179 nests with completed clutches)were parasitized by redheads (A. americana), other canvasbacks,or both, with an average of 4.7 parasitic eggs per parasitizednest. Parasitism had significant negative effects on the reproductivesuccess of nesting canvasbacks, although the proximate mechanismsinvolved differed from those operating in altricial species.Accidental displacement of eggs when parasitic females forcedtheir way onto host nests was the principal negative effectof parasitism, reducing the number of host eggs that were incubatedand ultimately hatched. Parasitism by redheads was relativelymore costly to canvasbacks than was intraspecific parasitism,with approximately 0.31 and 0.17 host eggs displaced per parasiticredhead and canvasback egg laid, respectively. No additionalnegative effects of parasitism on the hatchability of host eggsoccurred subsequent to parasitic laying. Posthatch survivalof canvasback ducklings was lower in broods from parasitizednests but was unrelated to the presence or absence of redheadducklings. Canvasback hosts resisted intrusions by parasiticfemales but showed no evidence of discrimination against parasiticeggs or ducklings. Because most costs of parasitism in thissystem are inflicted at the time of parasitic laying, subsequentrejection of parasitic eggs or ducklings is probably of littlebenefit to canvasback hosts, while the evolution of behaviorthat might prevent parasitic laying in the first place, suchas more vigorous nest defense, may be constrained by its highcosts     

河南民权湿地公园青头潜鸭越冬行为模式及性别差异

为了更深入地了解青头潜鸭的越冬行为模式及性别差异,以期为后续青头潜鸭的保护管理提供科学的理论参考,2018年11-12月采用定点观察法、扫描取样法等方法,对河南民权国家湿地公园越冬期青头潜鸭的越冬行为模式及性别差异进行了观察分析。观察期间共记录到青头潜鸭158只,超过全球种群数量1000只的10%。分析结果表明：（1）民权湿地公园,青头潜鸭越冬期行为时间分配以静息、觅食和运动三类行为为主,其次是修整和飞行两类行为;运动行为与觅食、修整、社会等行为之间呈极显著正相关,修整行为与社会行为之间呈极显著正相关,静息行为与修整、运动、社会等行为之间呈极显著负相关,飞行行为与觅食、静息、修整等行为之间呈极显著负相关;（2）静息行为具有全时段高时间分配的特征,不存在峰期和谷期;觅食行为（峰期为10：30-11：30、13：30-14：30,谷期为11：30-12：30、14：30-15：30）和飞行行为（峰期为11：30-12：30、14：30-15：30,谷期为10：30-11：30、13：30-14：30、15：30-16：30）具有明显的错峰式节律;（3）不同性别青头潜鸭越冬行为时间分配存有差异,其中静息、觅食、运动是雄性青头潜鸭主要行为类别（超过70%）,雌性青头潜鸭的主要行为为运动、飞行、觅食（接近70%）;雌雄青头潜鸭在静息、修整、运动和飞行四类行为时间分配方面存在显著性差异,雄性的静息、修整行为的时间分配极显著高于雌性,而运动、飞行行为的时间分配极显著低于雌性;（4）不同性别青头潜鸭越冬行为活动节律方面,除飞行行为外,其余行为均在行为峰期与谷期节律方面存有差异。进一步分析表明：民权湿地公园青头潜鸭越冬行为模式符合行为投资与收益的能量学理论,越冬行为模式在行为时间分配和行为节律方面存在性别差异。     

Lesser Scaup Breeding Probability and Female Survival on the Yukon Flats,Alaska

ABSTRACT Information on the ecology of waterfowl breeding in the boreal forest is lacking, despite the boreal region's importance to continental waterfowl populations and to duck species that are currently declining, such as lesser scaup (Aythya affinis). We estimated breeding probability and breeding season survival of female lesser scaup on the Yukon Flats National Wildlife Refuge, Alaska, USA, in 2005 and 2006. We captured and marked 93 lesser scaup with radiotransmitters during prelaying and nesting periods. Although all marked lesser scaup females were paired throughout prelaying and incubation periods, we estimated breeding probability over both years as 0.12 (SE = 0.05, n = 67) using telemetry. Proportion of lesser scaup females undergoing rapid follicle growth at capture in 2006 was 0.46 (SE = 0.11, n = 37), based on concentration of yolk precursors in blood plasma. By combining methods based on telemetry, yolk precursors, and postovulatory follicles, we estimated maximum breeding probability as 0.68 (SE = 0.08, n = 37) in 2006. Notably, breeding probability was positively related to female body mass. Survival of female lesser scaup during the nesting and brood-rearing periods was 0.92 (SE = 0.05) in 2005 and 0.86 (SE = 0.08) in 2006. Our results suggest that breeding probability is lower than expected for lesser scaup. In addition, the implicit assumption of continental duck-monitoring programs that all paired females attempt to breed should be reevaluated. Recruitment estimates based on annual breeding-pair surveys may overestimate productivity of scaup pairs in the boreal forest.     

Foraging behavior of redheads (Aythya americana) wintering in Texas and Louisiana

Redheads, Aythya americana, concentrate in large numbers annually in traditional wintering areas along the western and northern rim of the Gulf of Mexico. Two of these areas are the Laguna Madre of Texas and Chandeleur Sound of Louisiana. We collected data on 54,340 activities from 103 redhead flocks in Texas and 51,650 activities from 57 redhead flocks in Louisiana. Males and females fed similarly, differing neither in levels of feeding (percent of all birds in flock that were feeding) (p>0.90) nor in percentages of birds feeding by diving, tipping, dipping, or gleaning from the surface (p>0.10). The foraging level of redheads in the upper Laguna Madre region was relatively constant throughout two winters. Foraging of redheads in early winter in Louisiana was significantly greater than redhead foraging in the upper Laguna Madre, but by late winter, foraging by redheads in Louisiana had declined to the same level as that shown by redheads foraging in the upper Laguna Madre. The overall foraging level of redheads from Chandeleur Sound was greater (41%) than that of redheads in the upper Laguna Madre (26%), yet it was quite similar to the 46% foraging level reported for redheads from the lower Laguna Madre. Redheads in the upper Laguna Madre region of Texas fed more by diving than did those in the Chandeleur Sound and the lower Laguna Madre. Diving increased in frequency in late winter. Greater reliance by redheads on diving in January and February indicates that the birds altered their foraging to feed in deeper water, suggesting that the large concentrations of redheads staging at this time for spring migration may have displaced some birds to alternative foraging sites. Our results imply that the most likely period for food resources to become limiting for wintering redheads is when they are staging in late winter.     

白眼潜鸭秋季行为时间分配及活动节律

2012年7~11月,采用焦点动物取样法和瞬时扫描法,在乌鲁木齐近郊水域白湖,对白眼潜鸭（Aythya nyroca）秋季行为进行实地观察研究。制定出白眼潜鸭行为谱,各种行为有取食、保养、运动、休息、警戒、其他,共6类14种。昼间各行为时间分配依次为取食（56.7%）、运动（13.8%）、保养（11.8%）、休息（11.2%）、警戒（5.1%）、其他（1.4%）。其中取食、休息、运动行为有明显的节律性变化。休息行为以家庭为单位聚集在一起进行,取食行为则分开进行。7~9月份7：00~8：00时、18：00~19：00时休息行为出现峰值,10~11月份8：00~9：00时、17：00~18：00时出现峰值;7~9月份取食行为在8：00~9：00时、17：00~18：00时有明显的峰值,10~11月份在10：00~11：00时和15：00~16：00时出现峰值;7~11月份运动行为均在中午达到峰值。白眼潜鸭7~9月份与10~11月份觅食行为、休息行为和保养行为差异极显著（P<0.01）,运动行为无显著性差异（P >0.05）。迁徙前（10月中旬）,白眼潜鸭有集群现象,数量最多达到37只,10月下旬种群集体迁徙。秋季白眼潜鸭主要时间用于取食,意图为了迁徙或越冬积累能量,集群迁徙有利于种群防御天敌。     

Possible competitive interactions between overwintering tufted duck (Aythya fuligula (L.)) and fish populations of Lough Neagh,Northern Ireland: evidence from diet studies

The overwintering population of tufted duck (Aythya fuligula) on Lough Neagh, Northern Ireland, has varied over the last three decades, with numbers declining in the early 1980s but then increasing to former levels in the late 1980s. Population fluctuations of recently introduced roach (Rutilus rutilus) mirrored these trends. The present study explores the possibility that competition for benthic food resources is responsible for these changes by examining the diets of tufted duck, roach and other major fish species of the lake. Diet overlaps were generally high due to the common consumption of chironomid larvae. The diet of tufted duck overlapped most with that of roach because these two species were the only significant consumers of molluscs. This evidence provides further support for a tufted duck — roach competition hypothesis.     

Redhead reproductive strategy choices: a dynamic state variable model

Female redhead ducks (Aythya americana) exhibit one of the highest frequenciesof facultative parasitic egg laying, extending reproductive choiceswithin a season beyond nesting only. The occurrence of alternative strategieson a population level within and among years and the factorsthat influence choices are not well documented or understood.We developed a dynamic state variable model to predict reproductivestrategy choice and the influence of female age, body mass,food availability, and host availability on strategy choice.The model predicts a general distribution of strategy choiceby body mass and a strong influence of both age and host availability onstrategy choice. As body mass increases, females choose morecostly reproductive strategies from nonbreeding to parasitizingto nesting to a dual strategy, which is defined as a parasiticallylaid clutch of eggs followed by another clutch laid in the females'own nest. Comparatively, food availability only influenced strategychoice by slightly increasing the use of more costly strategies.Predictions of strategy choice by body mass reflect relationships similarto those proposed by others. Previous studies of the influenceof food availability on observed parasitic frequencies producedmixed and often conflicting results. We propose that femaleredheads are assessing the host environment before making reproductivechoices and food availability functions to fine tune this assessmentby encouraging or discouraging more costly strategies at a lowerbody mass.     

Vigilance while sleeping in the breeding Pochard Aythya ferina according to sex and age

Capsule Peek rate was found to vary with sex and age and between drifting and immobile.