Molting Areas Research Articles

Harlequin Ducks in Québec

In the last decade, several survey and research efforts have been undertaken to better understand the ecology and distribution of Harlequin Ducks (Histrionicus histrionicus) in Québec. The results of these efforts are summarized and new survey, research and management needs are identified. Harlequin Ducks breed on rivers and streams of the Gaspé Peninsula, the Québec North Shore, and the immense Hudson Bay and Ungava Bay drainage basins. Québec is possibly the most important breeding area for Harlequin Ducks in eastern Canada, and there is every indication that a significant proportion of the birds wintering in south-western Greenland and in eastern North America breed in Québec. In spring, significant numbers of birds spend a few days or weeks along the Gaspé Peninsula before departing for their breeding or molting areas. The most important molting sites in Québec are Bonaventure Island, the Port-Daniel/Newport area, and the Pointe du Sud-Ouest/Jupiter River area on Anticosti Island. Known fall staging areas include the coastal waters of the Gaspé Peninsula, the Pointe du Sud-Ouest/Jupiter River area, and Brion Island, on the Magdalen Islands. The few Harlequin Ducks that overwinter in Québec are mostly in Baie des Chaleurs, on the south shore of the Gaspé Peninsula. There are no good data on trends of Harlequin Ducks in Québec. Major threats to population recovery/health include hydroelectric developments, illegal and subsistence harvests, coastal exploitation (aquaculture, fisheries, boating), and recreational activities on breeding rivers and streams. Survey, research and management needs include better estimates of breeding densities and distribution, characterization of spring, summer and fall coastal habitats, comprehensive genetic analysis, monitoring, and public education on the status of Harlequin Ducks.

New Insights on Harlequin Duck Population Structure in Eastern North America as Revealed by Satellite Telemetry

Abstract In order to better delineate affiliations between breeding, molting, and staging areas of the small Harlequin Duck (Histrionicus histrionicus) population wintering in eastern North America, in April 2001 satellite transmitters were implanted in eight adult males at Isle au Haut, Maine, a major wintering area for this population. Two birds were confirmed breeding on rivers on the Gaspe Peninsula, Quebec, two birds molted in northern Labrador, and four birds migrated to southwestern Greenland during the molting season, including one bird that bred in Quebec. The four birds tracked to southwestern Greenland likely molted there, although molting could be confirmed for only one bird. All birds tracked to Greenland, to breeding areas, and to molting locations returned to wintering sites in Maine the following wintering season. This study is the first confirmation of wintering male Harlequin Ducks from eastern North America molting in Greenland.

Eastward moult migration of non-breeding pink-footed geese (Anser brachyrhynchus) in Svalbard

Six adult male pink-footed geese ( Anser brachyrhynchus ), tagged with satellite transmitters, were tracked in Svalbard during the period of June–September in 2003 and 2004. The purpose of the study was to describe the movements and staging periods of individual geese during the post-breeding period to investigate a possible moult migration among pink-footed geese in Svalbard. All geese moved about 200 km east from their potential breeding (summering) areas in western Spitsbergen. The preferred moulting area was the island of Edgeøya, where four geese staged prior to a southward autumn migration. Five geese left potential breeding areas between 11 and 30 June, and remained for more than 25 days in eastern areas during most of July, which we interpret as the moult migration of either failed or non-breeders. Geese left moulting areas in mid-August, using an average of 1.4 staging areas before the autumn migration, suggesting that moult sites support pre-migration hyperphagia. Only one goose remained at the suspected breeding site from early June to early September. Mean monthly temperatures in the summering and moulting ranges of the geese were calculated from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. The mean June moult range temperature ( ? 0.9 ° C) was significantly lower than that of the summering ranges (4.6 ° C). The July mean moult range temperature did not differ significantly from that in June on the summering ranges. We contend that failed or non-breeding pink-footed geese move eastward in Svalbard to exploit the early stages of summer plant growth as a result of the delayed thaw compared with central and southern Spitsbergen.

Eastward moult migration of non-breeding pink-footed geese (Anser brachyrhynchus) in Svalbard

Six adult male pink-footed geese ( Anser brachyrhynchus ), tagged with satellite transmitters, were tracked in Svalbard during the period of June–September in 2003 and 2004. The purpose of the study was to describe the movements and staging periods of individual geese during the post-breeding period to investigate a possible moult migration among pink-footed geese in Svalbard. All geese moved about 200 km east from their potential breeding (summering) areas in western Spitsbergen. The preferred moulting area was the island of Edgeoya, where four geese staged prior to a southward autumn migration. Five geese left potential breeding areas between 11 and 30 June, and remained for more than 25 days in eastern areas during most of July, which we interpret as the moult migration of either failed or non-breeders. Geese left moulting areas in mid-August, using an average of 1.4 staging areas before the autumn migration, suggesting that moult sites support pre-migration hyperphagia. Only one goose remained at the suspected breeding site from early June to early September. Mean monthly temperatures in the summering and moulting ranges of the geese were calculated from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. The mean June moult range temperature ( ? 0.9 ° C) was significantly lower than that of the summering ranges (4.6 ° C). The July mean moult range temperature did not differ significantly from that in June on the summering ranges. We contend that failed or non-breeding pink-footed geese move eastward in Svalbard to exploit the early stages of summer plant growth as a result of the delayed thaw compared with central and southern Spitsbergen.

Demography, Genetics, and the Value of Mixed Messages

AbstractIverson et al. (2004) used estimates of the homing rate for molting adult Harlequin Ducks (Histrionicus histrionicus) in Alaska to draw inferences about population structure. Homing rates, defined as one minus the ratio of birds recaptured elsewhere to those recaptured at the original banding site, were high (0.95–1.00) for males and females. Iverson et al. (2004) concluded that these high rates of homing are indicative of demographic independence among molting groups separated by small distances (tens to hundreds of kilometers) and that conservation efforts should recognize this fine-scale population structure. We re-examined their use of the homing rate, because their assumption of equal detection probability across a wide sampling area could have led to an upward bias in their estimates of site fidelity. As a result, we are hesitant to agree with their conclusion of high adult homing to molting areas and that molt-site fidelity is evidence for demographic independence. Our hesitancy stems from the fact that little is known about juvenile and adult movements within and among years, breeding area origins, and the variation of demographic parameters (e.g., survival and productivity) among molting groups. Furthermore, population genetic data of these molting groups suggest gene flow at both nuclear and mitochondrial loci. Such mixed messages between demographic (i.e., banding) and genetic data are increasingly common in ornithological studies and offer unique opportunities to reassess predictions and make more robust inferences about population structure across broad temporal and spatial scales. Thus, we stress that it is this broader scale perspective, which combines both demography and genetics, that biologists should seek to quantify and conservation efforts should seek to recognize.

Traversing a Boreal Forest Landscape: Summer Movements of Tule Greater White-fronted Geese

We monitored the movement, distribution and site affinities of radio-marked Tule Greater White-fronted Geese (Anser albifrons elgasi) during spring and summer in Alaska, 1994-1997 and 2004. Our assessment of summer movements was comprehensive, as locations were obtained during prenesting, nesting, and molt for over 90% of geese with active radios captured during winter or the previous summer in Alaska. Geese arrived to coastal and interior marshes in the Cook Inlet Basin (CIB) from mid April to early May, after which they moved to nesting areas in the upper CIB. Nesting birds used coastal staging areas in close proximity to eventual nest site location. Molting sites included a sub-glacial lake system in the upper CIB, although up to 50% of geese underwent a molt migration to wetlands across the Alaska Range, 400-600 km west of the CIB. Geese that molted at distant sites returned to the CIB before autumn migration. Length of stay in the CIB varied among years from 108-119 days, and averaged 116 days. Summer home-range sizes, exclusive of molting areas, averaged >273,000 ha, and were substantially larger than reported for other northern-nesting waterfowl. No radio-marked geese were found nesting in the vicinity of Redoubt Bay on the west side of Cook Inlet, and few nested near the Susitna Flats, the only other previously known nesting areas. The absence of nesting geese from Redoubt Bay corroborates aerial survey data showing a precipitous decline in the use of the west side of Cook Inlet between the early 1980s and early 1990s. The change in distribution of geese is likely related to a major eruption of Redoubt Volcano in 1989 that significantly altered landscapes used by nesting, brood rearing, and molting geese in the vicinity of Redoubt Bay. High inter-site movements of Greater White-fronted Geese throughout summer in south central Alaska likely increases exposure to predation, but also promotes social interactions and facilitates pioneering of distant, and diverse habitats in a vast, patchy, and often unpredictable landscape.

DEMOGRAPHY, GENETICS, AND THE VALUE OF MIXED MESSAGES

Abstract Iverson et al. (2004) used estimates of the homing rate for molting adult Harlequin Ducks (Histrionicus histrionicus) in Alaska to draw inferences about population structure. Homing rates, defined as one minus the ratio of birds recaptured elsewhere to those recaptured at the original banding site, were high (0.95–1.00) for males and females. Iverson et al. (2004) concluded that these high rates of homing are indicative of demographic independence among molting groups separated by small distances (tens to hundreds of kilometers) and that conservation efforts should recognize this fine-scale population structure. We re-examined their use of the homing rate, because their assumption of equal detection probability across a wide sampling area could have led to an upward bias in their estimates of site fidelity. As a result, we are hesitant to agree with their conclusion of high adult homing to molting areas and that molt-site fidelity is evidence for demographic independence. Our hesitancy stems from...

Use of trace elements in feathers of sand martinRiparia ripariafor identifying moulting areas

We investigated whether trace elements in tail feathers of an insectivorous and long‐distance migratory bird species could be used to identify moulting areas and hence migratory pathways. We analysed tail feathers from birds of different age and sex collected from a range of different breeding sites across Europe. The site of moult had a large effect on elemental composition of feathers of birds, both at the European and African moulting sites. Analysis of feathers of nestlings with known origin suggested that the elemental composition of feathers depended largely upon the micro‐geographical location of the colony. The distance between moulting areas could not explain the level of differences in trace elements. Analysis of feathers grown by the same individuals on the African wintering grounds and in the following breeding season in Europe showed a large difference in composition indicating that moulting site affects elemental composition. Tail feathers moulted in winter in Africa by adults breeding in different European regions differed markedly in elemental composition, indicating that they used different moulting areas. Analysis of tail feathers of the same adult individuals in two consecutive years showed that sand martins in their first and second wintering season grew feathers with largely similar elemental composition, although the amounts of several elements in tail feathers of the older birds was lower. There was no difference between the sexes in the elemental composition of their feathers grown in Africa. Investigation of the trace element composition of feathers could be a useful method for studying similarity among groups of individuals in their use of moulting areas.

Timing and Location of Wing Molt in Horned, Red-necked and Western Grebes in North America

Abstract We document timing and location of wing molt in the Horned Grebe (Podiceps auritus), Red-necked Grebe (Podiceps grisegena), and Western Grebe (Aechmophorus occidentalis). Horned Grebes left breeding ponds in late May to August and were observed on large ponds and lakes (near breeding locations) where they replaced remiges before progressing to wintering areas in September and October. Red-necked Grebes moved to much larger bodies of water such as the Great Lakes and the coast following breeding and prior to molt. On the Pacific Coast, Boundary Bay, British Columbia was identified as a major molt site. Freshwater molting areas were identified around Manitoulin Island in northern Lake Huron. On the Atlantic coast, molt sites were located in the Gulf of St. Lawrence. Western Grebes were found in wing molt at both large freshwater lakes and coastal locations (including Boundary Bay, British Columbia). Like the Great Crested Grebe (P. cristatus) and Eared Grebe (P. nigricollis), Horned, Red-necked and...

Abundance and Distribution of Harlequin Ducks Molting in Eastern Canada

Until recently, very little was known about the basic ecology of the Harlequin Duck (Histrionicus histrionicus) in eastern North America, including molting locations. A combination of aerial, ground and boat surveys were initiated in 1989 (Québec) and 1994 (Newfoundland and Labrador), and continued through 1999, to locate their molting areas. Molting Harlequin Ducks were found in Labrador, Newfoundland and the Gaspé Peninsula and Anticosti Island, Québec. Coastal areas of southern Labrador, Grey Islands, northern Newfoundland, and Bonaventure and Anticosti Islands, southern Québec, were the most important sites. The tip of northern Labrador and possibly sites along the Québec North Shore and Greenland are the most likely sites where the rest of the eastern population molts. Molting chronology for the ducks in Québec is similar to those on the east and west coast of North America. Now that these sites are known, monitoring and, if necessary, protection of these sites can be considered.

Relationship Among Breeding, Molting, and Wintering Areas of Male Barrow's Goldeneyes (Bucephala Islandica) in Eastern North America

Abstract Little is known of the eastern North American population of Barrow's Goldeneyes (Bucephala islandica), which was recently listed as “of special concern” in Canada. In 1998 and 1999, we marked 18 adult males wintering along the St. Lawrence River, Québec, with satellite transmitters to document their breeding, molting, and wintering distribution and phenology, and to describe timing and routes of their spring, molt, and fall migrations. Thirteen males moved inland from the St. Lawrence River to breed; the spring migration averaged 5.9 days, and birds arrived on breeding areas on average 9 May. All breeding areas were inland, on the north shore of the St. Lawrence River estuary and gulf. Breeding areas averaged 64.8 km from the St. Lawrence corridor. Males stayed on their respective breeding area a mean of 34.5 days, and left on average 11 June. Twelve males were tracked to their molting areas, one of which stayed on its wintering area until 5 June and flew directly to its molting area. Their molt migration averaged 18.6 days, and the mean arrival date on molting areas was 30 June. All molting areas were located north and averaged 986 km from breeding areas. Four males molted in Hudson Bay, four in Ungava Bay, two in northern Labrador, one on Baffin Island, and one inland, near the Québec–Labrador border. The mean length of stay on the molting areas was 105.3 days, and the mean date of departure from molting areas was 4 October. All goldeneyes for which the radio still functioned during fall migration returned to winter in the St. Lawrence River estuary, on average 6 November. Our results refute the idea that the main breeding area of the eastern North American population of Barrow's Goldeneyes is located in northern Québec and Labrador and rather indicate that it is in the boreal forest just north of the St. Lawrence River estuary and gulf. They also indicate that Barrow's Goldeneye males undertake a genuine molt migration, and highlight the importance of molting areas because birds stayed there approximately four months each year.

Relationship among Breeding, Molting, and Wintering Areas of Male Barrow's Goldeneyes (Bucephala islandica) in Eastern North America

Little is known of the eastern North American population of Barrow's Goldeneyes (Bucephala islandica), which was recently listed as “of special concern” in Canada. In 1998 and 1999, we marked 18 adult males wintering along the St. Lawrence River, Québec, with satellite transmitters to document their breeding, molting, and wintering distribution and phenology, and to describe timing and routes of their spring, molt, and fall migrations. Thirteen males moved inland from the St. Lawrence River to breed; the spring migration averaged 5.9 days, and birds arrived on breeding areas on average 9 May. All breeding areas were inland, on the north shore of the St. Lawrence River estuary and gulf. Breeding areas averaged 64.8 km from the St. Lawrence corridor. Males stayed on their respective breeding area a mean of 34.5 days, and left on average 11 June. Twelve males were tracked to their molting areas, one of which stayed on its wintering area until 5 June and flew directly to its molting area. Their molt migration averaged 18.6 days, and the mean arrival date on molting areas was 30 June. All molting areas were located north and averaged 986 km from breeding areas. Four males molted in Hudson Bay, four in Ungava Bay, two in northern Labrador, one on Baffin Island, and one inland, near the Québec–Labrador border. The mean length of stay on the molting areas was 105.3 days, and the mean date of departure from molting areas was 4 October. All goldeneyes for which the radio still functioned during fall migration returned to winter in the St. Lawrence River estuary, on average 6 November. Our results refute the idea that the main breeding area of the eastern North American population of Barrow's Goldeneyes is located in northern Québec and Labrador and rather indicate that it is in the boreal forest just north of the St. Lawrence River estuary and gulf. They also indicate that Barrow's Goldeneye males undertake a genuine molt migration, and highlight the importance of molting areas because birds stayed there approximately four months each year.

RELATIONSHIP AMONG BREEDING, MOLTING, AND WINTERING AREAS OF MALE BARROW'S GOLDENEYES (BUCEPHALA ISLANDICA) IN EASTERN NORTH AMERICA

Little is known of the eastern North American population of Barrow's Goldeneyes (Bucephala islandica), which was recently listed as “of special concern” in Canada. In 1998 and 1999, we marked 18 adult males wintering along the St. Lawrence River, Québec, with satellite transmitters to document their breeding, molting, and wintering distribution and phenology, and to describe timing and routes of their spring, molt, and fall migrations. Thirteen males moved inland from the St. Lawrence River to breed; the spring migration averaged 5.9 days, and birds arrived on breeding areas on average 9 May. All breeding areas were inland, on the north shore of the St. Lawrence River estuary and gulf. Breeding areas averaged 64.8 km from the St. Lawrence corridor. Males stayed on their respective breeding area a mean of 34.5 days, and left on average 11 June. Twelve males were tracked to their molting areas, one of which stayed on its wintering area until 5 June and flew directly to its molting area. Their molt migration averaged 18.6 days, and the mean arrival date on molting areas was 30 June. All molting areas were located north and averaged 986 km from breeding areas. Four males molted in Hudson Bay, four in Ungava Bay, two in northern Labrador, one on Baffin Island, and one inland, near the Québec–Labrador border. The mean length of stay on the molting areas was 105.3 days, and the mean date of departure from molting areas was 4 October. All goldeneyes for which the radio still functioned during fall migration returned to winter in the St. Lawrence River estuary, on average 6 November. Our results refute the idea that the main breeding area of the eastern North American population of Barrow's Goldeneyes is located in northern Québec and Labrador and rather indicate that it is in the boreal forest just north of the St. Lawrence River estuary and gulf. They also indicate that Barrow's Goldeneye males undertake a genuine molt migration, and highlight the importance of molting areas because birds stayed there approximately four months each year.

Using stable-isotope analysis of feathers to distinguish moulting and breeding origins of seabirds.

To determine whether stable isotope measurements of bird feathers can be used to identify moulting (interbreeding) foraging areas of adult seabirds, we examined the stable-carbon (δ13C) and nitrogen (δ15N) isotopic composition of feathers of chicks and adults of black-browed albatrosses (Diomedea melanophrys) from Kerguelen Islands, southern Indian Ocean. Albatross chicks are fed primarily fish (75% by mass), the diet being dominated by various species of the family Nototheniidae and Channichthyidae which commonly occur in the shelf waters in the vicinity of the colony. δ13C and δ15N values in chick feathers, which are grown in summer in the breeding area, were lower than values in adult feathers, which are grown in winter (δ13C: -19.6‰ versus -17.6‰ and δ15N: 12.4‰ versus 15.7‰, respectively). No differences in δ13C and δ15N values were found in adult wing feathers moulted in 1993 and 1994 and in adult feathers formed at the beginning, middle and end of the 1994 moulting period. These data are consistent with adults moulting in the same area and feeding at the same trophic level from one year to the next and with no major changes in foraging ecology within a given moulting season; they suggest that foraging grounds were different in summer and winter and that these differed in their stable-isotope signature. Changes in both feather δ13C and δ15N values indicated feeding south of the Subtropical Front (STF) during chick rearing, which is in agreement with the known foraging ecology at this time and feeding north of the STF during moult. This, together with band recoveries from adult birds, indicates that black-browed albatrosses from Kerguelen Islands wintered in subtropical waters off southern Australia. The stable-isotope markers in feathers, therefore, have the potential for locating moulting areas of migratory seabird species moving between isotopically distinct regions and for investigating seabirds' foraging ecology during the poorly known interbreeding period. Such information is needed for studies of year-round ecology of seabirds as well as for their conservation and the long-term monitoring of the pelagic environment.

At-Sea Distribution of Spectacled Eiders: A 120-Year-Old Mystery Resolved

The at-sea distribution of the threatened Spectacled Eider (Somateriafischeri) has remained largely undocumented. We identified migration corridors, staging and molting areas, and wintering areas of adult Spectacled Eiders using implanted satellite transmitters in birds from each of the three extant breeding grounds (North Slope and Yukon-Kuskokwim Delta in Alaska and arctic Russia). Based on transmitter locations, we conducted aerial sur- veys to provide visual confirmation of eider flocks and to estimate numbers of birds. We identified two principal molting and staging areas off coastal Alaska (Ledyard Bay and east- ern Norton Sound) and two off coastal Russia (Mechigmenskiy Bay on the eastern Chukotka Peninsula, and the area between the Indigirka and Kolyma deltas in the Republic of Sakha). We estimated that >10,000 birds molt and stage in monospecific flocks at Mechigmenskiy and Ledyard bays, and several thousand molt and stage in eastern Norton Sound. We further identified eastern Norton Sound as the principal molting and staging area for females nest- ing on the Yukon-Kuskokwim Delta, and Ledyard Bay and Mechigmenskiy Bay as the prin- cipal molting and staging areas for females nesting on the North Slope. Males marked at all three breeding grounds molt and stage in Mechigmenskiy Bay, Ledyard Bay, and the Indi- girka-Kolyma delta region. Males from the Yukon-Kuskokwim Delta molt and stage mainly at Mechigmenskiy Bay. Equal numbers of males from the North Slope molt and stage at all three areas, and most males from arctic Russia molt and stage at the Indigirka-Kolyma delta region. Postbreeding migration corridors were offshore in the Bering, Chukchi, and Beaufort seas. In winter, eiders were in the Bering Sea south of St. Lawrence Island. Our estimates from surveys in late winter and early spring suggest that at least 333,000 birds winter in

Distribution, Abundance and Reaction to Aerial Surveys of Post-breeding King Eiders (<i>Somateria spectabilis</i>) in Western Greenland

Moulting and post-breeding king eiders in western Greenland were surveyed in late August and early September of 1993, 1994, and 1995. We counted all eiders observed during fixed-winged aircraft flights along coastlines and offshore transects. The coastline in the survey area is roughly 13 400 km long, and our flightlines totalled approximately 16 500 km. The areas optimal for the birds were covered fully several times; in less suitable areas, only a fraction of the coastline was covered. Using the largest count for coastlines covered more than once, we counted a total of 22 980 king eiders. Large numbers of king eiders were observed at a number of remote localities on the west coast of Disko Island and in southern Upernavik. At localities considered to have frequent disturbance, few birds were observed. Highest densities were found along coasts with sandy or muddy areas at the shorelines. Overall we estimate that 30 000 to 40 000 king eiders reside in the coastal zone of western Greenland in late August. Even allowing for a high turnover rate, as different individuals may occupy the moulting areas during the extended period from July to October, this figure can account for only half of a 1950s estimate that 200 000 males and immatures were moulting in western Greenland.

Migration and moult of Dunlin Calidris alpina wintering in the central Mediterranean

Dunlin migration in northeast Italy is described. An attempt to identify the main routes and staging areas used by birds wintering in the central Mediterranean is presented. The results of monthly counts from 1990–1995 revealed that the bulk of the population occupied the wintering area in October and left for the breeding grounds in April and May. The analysis of 342 Italian recoveries of foreign ringed birds showed that 65% were ringed during post-breeding migration through the Baltic Sea, whereas just a few birds had been ringed in western Europe. First-year birds arrived in autumn with a single migratory wave, peaking in October. Two categories of adults were identified during post-breeding migration: birds which directly reached Italian wintering sites and birds which arrived after they had suspended their migration for moulting: the Azov/Black Sea wetlands are suggested as possible moulting areas. Out of 2444 adults and 1627 first-years ringed between 1989 and 1996 at our study area, we obtained a total of 42 recoveries abroad and evidence of direct links between Azov/Black Sea and N Adriatic wetlands, both during autumn and spring migrations. Primary moult was observed only in adults arriving early, the second migratory wave being composed of moulted birds. Locally moulting adults adopted a moult strategy characterized by high raggedness scores, typical of resident moulters. Body mass was not affected by primary moult stage or intensity, winter mass values being reached two weeks after the average date of primary moult completion.

Cyclical Changes in Body Composition in the Annual Cycle and Migration of the Eared Grebe Podiceps nigricollis

In changes that are among the most dramatic known for birds, Eared Grebes undergo 3-6 atrophy/hypertrophy cycles in major body constituents annually. The most pronounced takes place at staging areas in fall, when grebes become flightless for up to several months. At this season they accumulate huge fat stores (to 46% of lean body mass) and more than double the mass of body, liver, stomach, and intestine; leg and heart mass also increase. Concurrrently, pectoral muscles atrophy and can shrink below the size needed for flight (11% of total body mass). Before grebes depart for wintering areas these changes are reversed. In a 2-3 week predeparture period body mass drops by one-third as birds catabolize fat and reduce viscera mass by ?50%; leg mass also declines, while pectoral muscle increases. Similar cycles, which do not involve fattening to obesity, are repeated at wintering and breeding locations and, in some birds, on additional spring staging and fall molting areas. Heavy fat deposits in fall may insure that grebes can postpone their migration to wintering areas into the months of maximum darkness, thereby minimizing the risk of predation. The extreme predeparture reductions in leg and visceral mass, which occur in all seasons, reduce flight costs by minimizing wing loading and enhancing flight speed. Why grebes allow pectoral muscles to atrophy if they must rebuild them presently remains a puzzle. Several lines of evidence suggest that grebes attain a specific (optimal?) body composition prior to migrating. Further research into changes that may take place in other species prior to migration or at different times of the annual cycle is warranted.

Nutritional Implications of Molt in Male Canvasbacks: Variation in Nutrient Reserves and Digestive Tract Morphology

Body composition and gut morphology of molting male Canvasbacks (Aythya valisineria) were investigated in central Alberta from termination of breeding activities until fall migration (May-October) in 1989-1990. During this postreproductive period, male Canvasbacks underwent prebasic, down, and partial prealternate molts. Protein, lipid, and mineral dynamics were analyzed to determine if male Canvasbacks relied on endogenous nutrient reserves to meet increased nutritional demands during molt. In addition, mass and length of digestive organs were analyzed to document changes in the digestive tract that could provide endogenous protein (i.e., via muscle tissue catabolism) and/or possibly enhance exogenous nutrient assimilation for molt. Ingesta-free body mass of male Canvasbacks reached its annual minima during remigial molt (x = 973.5 g) and fluctuated primarily in response to storage and catabolism of lipids. Body composition data indicated little reliance on endogenous fat, protein, and mineral to satisfy nutrient requirements for molt. Lipid reserves were not accumulated prior to molt, but instead were metabolized from arrival on molting areas through mid-remigial molt. Premigratory lipogenesis started during mid-remigial growth and occurred simultaneous to elevated molt intensity, indicating that energetic requirements for molt were met exogenously. Despite the relative stability of total body protein during postreproductive molts, there were marked shifts in the distribution of muscle tissue in molting birds. Pectoral muscles atrophied from arrival on molting habitat through mid-remigial molt, concurrent with hypertrophy of leg and some digestive tract tissues. Increased mass of the digestive tract during remigial molt originated principally from growth of the gizzard. The digestive tract returned to its original mass as birds regained the ability to fly and their diet reverted back to foods with lower fiber content. Because postreproductive molts were extended over six months, male Canvasbacks had relatively low daily nutritional demands that could be met by dietary intake.

Molt of Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain, Alaska

-I examined patterns and chronology of the prebasic molt and primary-feather growth rate of nonbreeding and postbreeding Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain, Alaska. I estimated molt intensity for adults and subadults of both sexes with molt rate (MR, proportion of feathers in blood quills) and percent new feathers (PN, proportion of feathers that recently completed growth) for 26 feather tracts. I then calculated mean total molt score (TMS) and mean total percent new score (TPN) for each sex, age class, molt stage (arrival, start, early, mid-, and late molt), and Julian date. TMS increased from arrival to early molt (14 June-22 July). Subadults molted at greater intensity than did adults during early, midand late molt (20 July-1 August); however, males and females in both age classes did not differ. TPN scores were significantly (P < 0.05) greater from 25 July to 1 August than from 20 to 22 July, primarily as a result of maturation of remiges and wing coverts. Brant replaced body and wing feathers concurrently. Back, rump, breast, and side regions were comprised of 25% or more blood quills in adults to 50% or more blood quills in subadults during the flightless period. Brant departing the molt area completed growth of only 11 to 21% of all feathers. Ninth-primary growth rate (x? = 7.2 ? SE of 0.1 mm/day) did not vary over sex and age classes nor between years (1988 vs. 1989). Remex growth rate declined significantly (P < 0.001) through molt but was not related to Julian date nor initial body mass. Most Black Brant began remex growth 4-10 July; however, some postbreeding adults did not arrive and start molt until 24-25 July. Brant made short flights when the ninth primary averaged 62% of its mean final length; sustained flight occurred at about 70% of completed growth. The duration of flightlessness was 23 and 24 days for females and males, respectively. Flightless Black Brant were present in the Teshekpuk Lake molting area from 26 June through 19 August. Upon regaining flight ability, Black Brant moved to coastal staging areas. The chronology and intensity of feather replacement for Black Brant may be important when determining the appropriate management of habitats where molt occurs, especially when these are disturbed by human activities. Received 16 August 1994, accepted 27 January 1995. THE POSTBREEDING PERIOD for migratory waterfowl is between reproduction and fall migration (Hohman et al. 1992; but see Fredrickson and Drobney 1979). During this stage, most ducks and geese molt wing and body feathers (Palmer 1976, Hohman et al. 1992:app. 5-1) and, subsequently, store adequate nutrient reserves for fall migration. Because postbreeding anatids are secretive and usually seek protective and inaccessible habitats during flightlessness (Fredrickson and Drobney 1979), little is known about the chronology, duration, or intensity of remigial molt. 1 Present address: Texas Parks and Wildlife Department, J. D. Murphree Wildlife Management Area, 10 Parks and Wildlife Drive, Port Arthur, Texas 77640, USA. Brood-rearing geese initiate remigial molt two to three weeks after their young hatch (Barry 1962, Owen and Ogilvie 1979). Failed breeders and nonbreeders often migrate to specific molting areas presumably to: (1) decrease the risk of predation and avoid human disturbance (Sterling and Dzubin 1967); (2) avoid competition with successful breeders molting on nesting areas (Salomonsen 1968); and/or (3) forage on higher-quality vegetation available at earlier growth stages in northern areas (Owen and Ogilvie 1979). In Black Brant (Branta bernicla nigricans), failed breeders and nonbreeders migrate from nesting areas along the Yukon and Kuskokwim river deltas (Alaska), the Canadian Arctic, and the Chukotski Peninsula (Russia) to the Teshekpuk Lake molting area on the Arctic Coastal Plain of Alaska (Derksen et al. 1979, 1982). Teshekpuk