Global ETD Search

1	Predation and antipredator tactics of nesting black brant and lesser snow geese Armstrong, William Terry 01 January 1998 (has links) Coloniality and nest defence were examined in black brant <i>Branta bernicla nigricans</i> and lesser snow geese Chen caerulescens caerulescens. Increased nest density had no effect on nest survival, egg survival, or likelihood of partial clutch predation in snow geese. In brant, nest survival declined as nest density increased in 1992 and with increased distance from shore in 1993. Brant with conspecific nearest neighbours were less likely to suffer partial clutch predation in 1993, but not in 1992. Egg survival in brant increased with nest density in 1993, but decreased as density increased in 1992, however, the decrease occurred only in nests with three or four eggs. Nesting at high densities, in central positions, or far from shorelines commonly travelled by glaucous gulls <i>Larurs hyperboreus</i> and parasitic jaegers <i>Stercorarius parasiticus</i>, the primary egg predators in this study, did not provide geese with a nest or egg survival advantage because effects were lacking in snow geese and were inconsistent and contradictory in brant. Female snow geese had very high nest attendance and both sexes had high territory attendance so snow goose nests were rarely unattended during incubation. Brant had lower nest attendance than snow geese, and due to a lack food near their nests, brant left their territories to feed resulting in lower territory attendance as well. Although male brant were capable of defending the nest from avian predators and usually remained on their territories when females were absent, males were less effective defenders than incubating females. Increased vigilance and decreased resting by female brant as incubation progressed provided support for the prediction, from parental investment theory, that nest guarding effort would increase with offspring age, but there were no changes in male brant or in snow geese. However, declining nest and territory attendance by female brant and males of both species contradicted predictions from parental investment theory but were consistent with an increased need to forage as nutrient reserves declined through incubation as expected due to energetic constraints. coloniality nesting biology wildlife biology incubation behaviour nest defence
2	Role znaků a geonů v rozpoznávání predátorů netrénovanými ptáky: obrana hnízda NOVÁKOVÁ, Nela January 2016 (has links) I examined two main hypotheses proposed for the object recognition: Particulate feature theory and recognition by components using methods of behavioural ecology, namely nest defence. We tested reactions of Red-backed shrike (Lanius collurio) to dummies of Common kestrel (Falco tinnunculus) with scrambled body parts (head above, in the middle and at the bottom). Our result suggested that birds don't recognize the kestrel in the dummies with inappropriately placed head. Therefore, our results support rather the theory recognition by components.
3	Nesting and migration in the introduced Canada goose in Sweden Sjöberg, Göran January 1993 (has links) The aim of the thesis was to document patterns in breeding and migration in Swedish Canada geese Branta canadensis, to explain these against the genetic and historical background of the population, and to test predictions of hypotheses pertaining to parental investment. The Canada goose population in Sweden was founded by the introduction of a few individuals in the 1930's. DNA fingerprint similarity between geese breeding in Sweden was on average at the same level as between inbred close relatives in other wild bird species. The genetic variability of the population appeared to be considerably reduced in comparison to that of Canada geese breeding in North America. Dispersal and migration patterns were studied using plastic neck-bands that could be identified at long distance. Most Canada goose females nested at the lake where they grew up. Males were more prone to disperse than females, although most of them still returned to breed close to their area of origin. Geese from three breeding areas in Sweden had different winter distributions, although wintering areas overlapped considerably. Individual geese tended to return to the same wintering area as they had used in previous years. The females' investment in the egg clutch was related to the migration distance from spring foraging areas to the nesting area, suggesting an energetic cost of migration for egg production. Within breeding seasons, clutch size decreased with later initiation of nesting, but only in years with early breeding. A probable reason for this decrease was that body reserves available for egg production were larger in early layers. In years with late breeding, clutch size did not decrease, most likely because late-nesting females could supplement their body reserves by foraging on fresh vegetation. Nest defence intensity was studied by recording the behaviour of the female geese when a human approached the nest. The results largely confirmed predictions for nest defence intensity extracted from parental investment theory. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 6 uppsatser</p> / digitalisering@umu Species introductions DNA fingerprinting natal dispersal breeding dispersal bird migration wintering areas clutch size laying date body reserves nest defence waterfowl Canada goose Anatidae Branta canadensis
4	Jak ťuhýk obecný (Lanius collurio) rozpoznává nepřátele / How the red-backed shrike (Lanius collurio) recognizes enemies NĚMEC, Michal January 2015 (has links) This study investigates two questions about anti-predator behaviour of the red-backed shrike. 1) Is the red-backed shrike able to assess the differing dangers represented by various types or species of predators? 2) How does the red-backed shrike recognize the predator? We found, that the red-backed shrike (Lanius collurio) adjusts its anti-predator behaviour by assessing the potential threat to themselves from different predator species and by assessing the chance of a successful attack. Further, we found that the presence of general raptor salient features is absolutely necessary for proper categorisation of the intruder as a predator, whereas the natural species-specific colouration in itself is an insufficient cue.
5	Antipredační chování ťuhýka obecného: role klíčových znaků v rozpoznávání predátora / Antipredatory behaviour of Red-backed Shrike: the role of sign stimuli in a predator recognition Součková, Tereza January 2011 (has links) This thesis summarizes findings on a recognition and categorization of different sorts of stimuli at birds, it deals with predator recognition in the Red-backed Shrike (Lanius collurio) in its practical part. The aim of my study was to examine if Red-backed Shrikes follow by sign stimuli or colour of stimulus during the predator recognition. I performed my research by means of experiments with dummies, I have observed antipredatory reactions of Red-backed Shrikes on various types of dummies which differ in the presence or absence of features of raptor or in the different coloration. I concluded according to Shrikes' reactions that during the predator recognition the information on sign stimuli playes the principal role, but only this information alone is not fully sufficient. Antipredatory behaviour of the Red-backed Shrike was also influenced by sex of bird apart from type of dummy, males were more active during the nest defence than females.
6	Adaption an Nestprädation bei der Mönchsgrasmücke / Adaptations to nest predation in the blackcap Schaefer, Thomas 25 April 2002 (has links) No description available. 570 Biowissenschaften, Biologie Mathematics and Computer Science Video Neststandort Risikoverteilung Nachlegen Verhalten Fotofalle Multiprädatoreneffekt Rabenvögel Fragmentierung Gelegegröße Nestverteidigung Naturschutz Nestverluste Prädation Adaption Evolution Lebenszyklusmerkmale Video nestsite bet hedging relaying behaviour phototrap multi predator effect fragmentation clutch size nest defence conservation nest losses predation adaptation life history traits 42.83 42.65 WN000 WS

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