The resting postures, locomotion, feeding behaviour, and comfort movements of five species of grebes (Podiceps caspicus, P. auritus, P. grisegena, Podilymbus podiceps, and Aechmophorus occidentalis) are described, compared, and their development traced to the adult form. Each pattern is then compared with its counterpart in other groups of birds, and its adaptive significance is considered. In defecation, climbing-up, and begging the eliciting stimuli are examined. The stages of development are traced, and it is found that the birds hatch at the beginning of stage two, the first appearance of comfort movements. They pass into stage three, the maturation of comfort movements, within a few hours and remain in this stage until the adult sleep posture is assumed, functional preening and oiling are established, and spontaneous swimming appears, at eight days. Stage four includes the appearance of simple bathing, diving, and the substitution of following for riding on the parent’s back. Stage five, beginning about the sixteenth day includes matured bathing, alarm, self-feeding, and finally flight. Because of the great increase in length of stage three over that of precocial birds, the inability of the chicks to maintain the adult sleep posture, the lack of functional preening and oiling, and the depression of all activity, it is suggested that the grebes be considered not precocial birds but semi-precocial birds with the gulls. They are adapted by these attributes and by the controlled defecation response to life in a nest. The grebe nest being unsuitable for prolonged brooding, the grebe broods its chicks on its back. / Science, Faculty of / Zoology, Department of / Graduate

The present study describes and analyses the elements involved in the reproductive behaviour of the Eared Grebe and the relationships between these elements. Two summers of observation and comparison with the published work on the Great Crested Grebe give some insight into these elements, their evolution, and their stimuli. Threat and escape behaviour have been seen in the courtship of many birds, and the threat-escape theory of courtship in general has been derived from these cases. In the two grebes described threat plays a much less important role than the theory prescribes, and may not even be important at all. In the two patterns where the evolutionary relationships are clear, the elements are those of comfort preening. In the three patterns in which there is still some doubt, all the elements can be related to general non-reproductive behaviour or to nesting patterns. When courtship tapers off, nesting behaviour takes its place. The timing of this change and of the nesting behaviour patterns is caused by a general climatic stimulus followed by a more particular behavioural one. Nest-building and egg-laying are the results of the gradual building up of the sexual condition during courtship. Egg laying, however, takes place only in warm, dry weather. If the weather changes for the worse during laying, the birds stop and wait. The effect of this double stimulus is to put the birds on the borderline between determinate and indeterminate layers. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Michigan, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 277-281).

In this study, I first describe distribution and abundance of breeding Eared Grebes {Podiceps nigricollis) in British Columbia. Second, I characterize and examine the relationships between nesting habitat and nest site selection on breeding group size. Finally, I. examine effects of colony size, nesting chronology and nesting synchrony on reproductive success at Eared Grebe colonies. I surveyed 421 wetlands in 1985 and 1986 and located 47 lakes used by nesting Eared Grebes. Those 47 lakes accomodated from a low estimate of 1761 to a high estimate of 4474 pairs. Breeding abundance, calculated from adult, nest and young counts, ranged from single pairs to more than 590 pairs per lake. Breeding took place in shallow lakes of various sizes, subject to extensive variations in water levels. Breeding abundance was positively correlated with lake area. Fewer breeding pairs utilized nesting areas close to shore (in shallower water) than nesting areas far from shore (in deeper waters). Nesting areas close to shore were found in smaller lakes and were used less often in consecutive years than nesting areas far from shore, presumably because of lower habitat predictability. An experiment with unattended artificial nests showed that nest predation was higher far from shore than close to shore. Nesting areas close to shore were used by small groups. These maximized concealment by being located in denser vegetation. Nesting areas far from shore were used by larger groups and were located in more open areas. On both years, adults arrived at nesting lakes in April and May, started laying on 27 May and departed from, nesting areas in late July and- early August. Nesting was significantly earlier and reproductive success per pair was significantly higher in 1985 than in 1986. A .stepwise multiple regression examined effects of colony-size, synchrony and chronology on nesting success. Only nesting chronology accounted for differences in nesting success. Late nesters were not birds attempting to renest. Instead, there appeared to be qualitative differences across colonies that were related to ages of breeders. Eared Grebe colonies are likely not formed from passive aggregation at limiting resources and there are likely no foraging benefits from colonial nesting. Nesting colonies could increase detection and mobbing of predators, but no evidence supported this. Anti-predator benefits of coloniality might have been masked by differences in breeding chronology and synchrony, or were missed because of low sample size. / Science, Faculty of / Zoology, Department of / Graduate

Canada’s boreal forest provides important breeding habitat for 12 to 14 million migratory birds annually. Nonetheless the ecology of boreal wetlands remains poorly understood. Over the last 40 years, rapid industrial development with little attention to conservation has been ongoing in the region. Apparent population declines of species, such as that of lesser scaup have raised concerns about the quality of western boreal wetlands. This is one of very few studies demonstrating patterns in brood-rearing habitat use by ducks and grebes in the Canadian western boreal forest. In this study, wetland characteristics associated with brood-rearing wetlands of American wigeon (Anas Americana), green-winged teal (Anas crecca), mallard (Anas platyrhynchos), lesser scaup (Aythya affinis), ring-necked duck (Aythya collaris), horned grebe (Pondiceps auritus), and red-necked grebe (Podiceps grisegena) were investigated on 75 wetlands near Yellowknife, NT, Canada. I used Principle Components and regression analyses to delineate patterns of habitat use by breeding water birds. Results indicate that physical characteristics of wetlands, area in particular, had stronger correlations with brood-rearing habitat then did invertebrate abundance. Invertebrate groups positively associated with brood-rearing wetlands included: Amphipoda, Pelecypoda, and or Ephemeroptera. Breeding diving ducks had negative iv associations with Dipteran abundance. Diving ducks and red-necked grebes were more strongly correlated with habitat variables then were dabbling ducks and horned grebes. Brood-rearing wetlands of the smallest birds in the study, green-winged teal and horned grebe, had the fewest and weakest associations with habitat variables. / xiii, 97 leaves ; 29 cm

Despite the hemispheric importance of Great Salt Lake (GSL) as a staging area for migratory birds, little is known about the resources that GSL provides to these birds, or how changes to the GSL ecosystem might impact the avian community. Three species of migratory waterbirds that stage at GSL are Wilson’s phalaropes (Phalaropus tricolor), red-necked phalaropes (Phalaropus lobatus), and eared grebes (Podiceps nigricollis). My objective for this research was to study the impacts of prey availability on the staging ecology of these species. In Chapter 2, I examined the use of GSL habitats by both species of phalaropes. In the high-salinity bays of GSL, phalaropes were most strongly associated with shallow water. In the low-salinity bay, there were no strong associations between phalarope presence and particular habitat characteristics. In Chapter 3, I analyzed the behaviors of phalaropes relative to prey densities. Phalaropes commonly foraged in Carrington Bay, which had the highest densities of brine fly (Ephydridae) adults, and in Farmington Bay, which had high densities of benthic macroinvertebrates. Foraging behavior differed between Wilson’s and red-necked phalaropes, with Wilson’s phalaropes spinning more often than red-necked phalaropes. In Chapter 4, I examined interannual and nightly variations in eared grebe fall migration departures in relation to prey availability and environmental conditions. Eared grebes began migration relatively early when lake temperatures were relatively warm, densities of brine shrimp (Artemia franciscana) adults were high, and densities of brine shrimp cysts were low. The likelihood that eared grebes would depart on a given night was positively associated with the average barometric pressure 12 hours prior to sunset. The resources provided by GSL support substantial proportions of the staging populations of phalaropes and eared grebes. Management efforts should seek to maintain the habitats and resources needed by phalaropes and eared grebes at GSL. Future large-scale diversions of freshwater may threaten GSL’s suitability as a staging area for these birds.

Eared Grebes (Podiceps nigricollis) are migratory birds that build their nests over water and in large groups called colonies. Their typical breeding range is in central southern Canada and northern United States; however, a previously uncertain number of Eared Grebes (grebes) also nest around the Great Salt Lake (GSL), Utah, at the southern edge of their breeding range. Little is known about the habitat requirements for grebe nesting colonies at such low latitudes and if they are different from colonies found elsewhere. My objectives for this research were to determine the status of the grebe nesting population as well as their habitat characteristics along the GSL in freshwater wetlands. I found over 4,280 grebe nests distributed among 35 colonies. Grebes built nests by mounding submerged aquatic vegetation (SAV) beginning the first week of June. The results from my habitat study show that grebes prefer to nest in areas with an average water depth of 48 cm, high invertebrate density, and abundant areas of floating SAV. Water depth and vegetation type at colony sites as well as timing of nesting and average number of eggs per nest of GSL colonies differed from colonies located at more northern latitudes. The differences in nesting could be attributed to the need to wait for SAV to grow and form mats on the water’s surface, or a need to wait for their food source to reach harvestable size. After grebes leave their nesting grounds, they stop at the GSL where they prepare for their final migration southward by consuming their fill of brine shrimp (Artemia franciscana). Brine shrimp are tiny invertebrates that are well-adapted to salty environments; they produce hard-walled eggs called cysts which are of great economic value and are commercially harvested from the GSL. I compared cyst viability, which is the percentage of cysts in a condition conducive to hatching, for cysts that had passed through the digestive tract of grebes and cysts samples obtained from the GSL. Only 30% of the cysts that had passed through grebes were viable, whereas 63% of cysts from the GSL were viable.