Brood Movements Research Articles

Mallard brood movements and survival in an urbanized landscape

AbstractWhen selecting a nest site, mallards (Anas platyrhynchos) balance differing habitat requirements for the nesting and brood‐rearing periods, such that the juxtaposition of these habitats in the landscape may influence the female's reproductive strategy and reproductive success. Mallard populations in the northeastern United States have declined since the mid‐1990s, and increasing urban development in this region may pose risks to broods and cause high duckling mortality. We assessed mallard brood and duckling survival in the urbanized landscapes of Connecticut, USA, and evaluated whether differences in brood movements, home ranges, and habitat use in urbanized areas influence brood survival. We monitored 32 mallard broods from females with global positioning system (GPS) transmitters in Connecticut in 2021 and 2022. Apparent brood survival to 30 days (0.48, n = 29 broods) was comparable to previous estimates in the Northeast (range = 0.21–0.72), but individual duckling survival (0.18, n = 257 ducklings) was lower than many previous estimates for this region (range = 0.14–0.44), suggesting this parameter warrants continued evaluation because it may be contributing to population declines in Connecticut and the greater Northeast region. Mallard females demonstrated different reproductive strategies and seemed to prioritize either high‐quality nesting habitat or proximity to high‐quality brood‐rearing habitat. High‐quality nesting habitat is not necessarily near high‐quality brood‐rearing habitat, and 61% (17/28) of females moved their ducklings an average of 1.1 ± 0.9 km (SD) shortly after hatch to a brood‐rearing site, often traveling along small streams. A similar proportion of successful (9/12) and failed (7/13) broods moved. We provide evidence of limited availability of brood‐rearing habitat, as females moved long distances to brood‐rearing wetlands and only 1 brood made additional inter‐wetland moves. Management actions that create or modify nesting and brood‐rearing habitat should consider connectivity between these sites; females may choose to nest away from wetlands to minimize exposure to predators but may depend on small streams for travel to brood‐rearing wetlands.

Identifying targets for conservation: the arrival and loss of Common Eider Somateria mollissima ducklings in an estuarine nursery

ABSTRACTCapsuleThe arrival of Common Eider Somateria mollissima ducklings into a reception and nursery area is a measure of breeding success and phenology but reveals gaps in knowledge for effective conservation.AimsEstuarine habitats are important wildlife areas but are continually under threat from human activities. Common Eiders may be an indicator species for monitoring the impacts of development in estuaries used by them as nursery areas. The aim of this study was to understand the arrival and distribution of ducklings in a commercial and recreational estuarine environment.MethodsCoquet Island, Northumberland, is a breeding site for Common Eiders at the southern limit of their range on the east coast of the UK. Numbers of ducklings arriving in the adjacent Coquet Estuary nursery area were monitored daily during the breeding season over a 27-year period from 1995 to 2021 inclusive.ResultsCounts of ducklings were higher overall in less disturbed parts of the estuary, but there were no consistent patterns of habitat use. First-arrival dates varied annually by up to 23 days. Daily arrival counts were affected by tide and, to a lesser extent, rain and wind direction. Observed arrivals each season correlated with counts of breeding females on Coquet Island. There was evidence for links between broader-scale weather conditions (North Atlantic Oscillation indices) and yearly variation in rates of duckling arrival. Arrivals were more synchronous in years when ducklings were late in arriving and supported theoretical predictions from modelling studies. There were high daily rates of duckling loss from the estuary which may have been a consequence of brood movements out of the estuary and loss to predation. There was a positive correlation between counts of ducklings and attendant females.ConclusionsAnnual duckling counts show the value of estuaries for monitoring phenological variation in the breeding of Common Eiders. A better understanding of environmental factors influencing duckling retention or loss in estuaries is needed. Enabling human and wildlife activities to exist together within estuarine environments may promote effective conservation.

Facultative polygamy may influence post-fledging movements in a brood-splitting passerine

Animal space-use patterns can vary widely with age, sex, and stage of the annual cycle, but the factors that drive pattern shifts are poorly understood. Here, we provide preliminary evidence that mating strategy (i.e., polygamy) influences movements of parents attending recently fledged young. We monitored the space use during the post-fledging period for Vermivora spp. broods led by a male and female with a split brood in 2014 and the same male with 2 fledglings in 2015. We observed contextand sex-specific space-use patterns that seemed to be driven by the male's attention to a secondary polygamous nest in 2014. When attending his secondary nest, the male restricted his primary brood's movements to within the nesting habitat close to his secondary nest until the nest failed. This pattern was distinct from movements of both the 2014 female and the same male in 2015 when he lacked a secondary nest. These observations may explain some reports from other studies that female-led broods disperse farther than male-led broods. Future work should explicitly consider the potential impacts of facultative polygamy on post-fledging space use, especially in species traditionally considered monogamous.

Brood rearing has an immediate survival cost for female Chinese Grouse Tetrastes sewerzowi

Reproductive activities can incur various costs to breeding individuals in birds. One cost is that reproduction decreases survival probabilities of attendant individuals, which may have a major effect on population demography. During brood rearing, adults of precocial species usually make extensive movements to lead their young to sites with adequate food resources and dense cover. However, few studies have evaluated the effects of brood movement on attendant precocial adults. In this study, we tracked female Chinese Grouse during brood-rearing periods using radiotelemetry at Lianhuashan Nature Reserve, Gansu, China, during 2010–2012, to evaluate the effects of brood rearing and movement distances on females’ survival probabilities using known fate models in program MARK. All 41 females attempted to breed, and 30 females successfully hatched at least one chick; 11 failed during the incubation period. Although females with broods moved more extensively than females without broods, movement distances did not influence survival probabilities of attendant females. Seven females with broods were killed by predators, resulting in a lower survival probability (0.958 ± 0.016 weekly survival and 0.679 ± 0.099 through the 9-weeks brood-rearing periods) than for females without broods, which all survived the brood-rearing periods. Our results agree with the prediction of life history theory, which assumes that cost must correlate with reproduction. The extensive movement patterns found in this study might reflect a lack of suitable brood-rearing habitat near nest sites, which might be detrimental to chick survival and influence the persistence of this population.

Weather, habitat composition, and female behavior interact to modify offspring survival in Greater Sage-Grouse.

Weather is a source of environmental variation that can affect population vital rates. However, the influence of weather on individual fitness is spatially heterogeneous and can be driven by other environmental factors, such as habitat composition. Therefore, individuals can experience reduced fitness (e.g., decreased reproductive success) during poor environmental conditions through poor decisions regarding habitat selection. This requires, however, that habitat selection is adaptive and that the organism can correctly interpret the environmental cues to modify habitat use. Greater Sage-Grouse (Centrocercus urophasianus) are an obligate of the sagebrush ecosystems of western North America, relying on sagebrush for food and cover. Greater Sage-Grouse chicks, however, require foods with high nutrient content (i.e.,forbs and insects), the abundance of which is both temporally and spatially dynamic and related primarily to water availability. Our goal was to assess whether nest site selection and movements of broods by females reduced the negative effect of drought on offspring survival. As predicted, chick survival was negatively influenced by drought severity. We found that sage-grouse females generally preferred to nest and raise their young in locations where their chicks would experience higher survival. We also found that use of habitats positively associated with chick survival were also positively associated with drought severity, which suggests that females reduced drought impacts on their dependent young by selecting more favorable environments during drought years. Although our findings suggest that female nest site selection and brood movement rates can reduce the negative effects of drought on early offspring survival, the influence of severe drought conditions was not completely mitigated by female behavior, and that drought conditions should be considered a threat to Greater Sage-Grouse population persistence.

Bobwhite Brood Ecology in Relation to Fallow Field Management Techniques and Prescribed Fire Regime

We used compositional analysis to rank habitats used by nesting and brood-rearing northern bobwhites (Colinus virginianus) in northern Florida. We used a residence index based on brood movement rates and turning angles to predict distribution of organisms among habitat types within brood ranges. We examined relationships among residence indices and vegetation and invertebrate characteristics of the habitat to draw inferences as to brood habitat quality. We related brood survival to vegetation, landscape structure and composition, and invertebrate characteristics within brood ranges. Finally, we reported effects of season of disking (fall vs spring) on vegetative (composition, canopy cover, density, ground cover) and invertebrate (richness and biomass) communities in fallow agricultural fields.

Habitat selection and movements of Piping Plover broods suggest a tradeoff between breeding stages

In precocial birds, adults select breeding areas using cues associated with habitat characteristics that are favorable for nesting success and chick survival, but there may be tradeoffs in habitat selection between these breeding stages. Here we describe habitat selection and intra-territory movements of 53 Piping Plover (Charadrius melodus) broods (320 observations) during the 2007–2008 breeding seasons on mainland- and island-shoreline habitats at Lake Sakakawea, North Dakota, USA. We used remotely sensed habitat characteristics to separately examine habitat selection and movements at two spatiotemporal scales to account for potential confounding effects of nest-site selection on brood-rearing habitat used. The scales used were (1) the entire brood-rearing period within available brood-rearing areas and (2) 2-day observation intervals within age-specific discrete habitat selection choice sets. Analyses at both scales indicated that broods selected areas which were non-vegetated, moderately level, and nearer to the shoreline. Rate of brood movement increased with age up to 5 days, then stabilized; broods that hatched >50 m away from the shoreline moved toward the shoreline. Brood movements were greater when they were in vegetated areas, when the brood-rearing area was of greater topographic complexity, and when broods aged 6–25 days were further away from the shoreline. Using inferences from our results and those of previously published work, we postulate how a potential tradeoff in habitat selection between nesting and brood-rearing can contribute to an ecological trap in a novel habitat. This work, in the context of published works, suggests that plover breeding habitat is a complex of both nesting and brood-rearing habitats and provides a basis for making remotely sensed abundance estimates of suitable breeding habitat for Piping Plovers.

Use of Nape Tags for Marking Offspring of Precocial Waterbirds

Abstract. Individualized markers that allow organisms to be identified without recapture are invaluable for studies of survival, movement, and behavior. Nape tags consisting of brass safety pins with unique combinations of two or three colored plastic beads were used to mark 5,868 American Coot (Fulica americana) chicks and 331 Ruddy Duck (Oxyura jamaicensis), 157 King Eider (Somateria spectabilis) and 664 White-winged Scoter (Melanitta fusca deglandi) ducklings. These markers allowed for documentation of parent-offspring interactions, post-hatching survival, brood movements and brood-mixing behaviors. Nape tags were inexpensive, easy to make, easy to observe with binoculars or spotting scopes and provided over 100 two-bead or 1,000 three-bead color combinations for individual identification. For coots, there was no evidence of color biases affecting parental care or offspring survival, although some colors (white, yellow) were easier to detect than others (brown). The only observed problem was marker los...

Reproductive Success and Brood Movements of Giant Canada Geese in Eastern South Dakota

Abstract The population of resident giant Canada geese (Branta canadensis maxima) has increased dramatically in eastern South Dakota since reintroduction efforts were initiated in the 1960s. In order to effectively manage this population of Canada geese, it is important to determine their reproductive success. We collected information on goose nesting success and related brood movements using Very High Frequency (VHF) telemetry. We captured Canada geese in seven counties in eastern South Dakota during summers, 2000–2003. The reproductive success of 88 females was monitored during spring 2001–2004. Half of the geese had successful nests, 20.5% were unsuccessful, and 29.5% did not attempt to nest. Apparent and Mayfield nesting success estimates averaged 71% and 63%, respectively. Overall egg success was 62.6% and overall hatching success was 88.8%. Mean total clutch size averaged 5.73 ± 0.17 while the number of goslings leaving the nest averaged 5.02 ± 0.25. Forty-nine percent of marked females nested on or...

Parental behaviour of a precocial species: implications for juvenile survival

Summary 1. Parents determine habitat selection for precocial young by leading their young to foraging areas until the chicks attain full independence. There are potential benefits and costs to reproductive success associated with changing habitats while caring for young. This study investigated the relationship between different types of habitats and their quality on chick survival and brood movements of a declining upland shorebird, the mountain plover Charadrius montanus. 2. From 2004 to 2006, a total of 153 mountain plover broods were monitored on the primary breeding habitats in eastern Colorado, USA; two shortgrass prairie habitats that were either occupied or unoccupied by black‐tailed prairie dogs Cynomys ludovicianus and agricultural lands. Habitat quality hypotheses were tested using newly developed statistical applications to estimate survival of chicks and brood movement patterns. 3. Chick survival and brood movements were influenced by habitat. Chick survival over the 30‐day brood‐rearing period was substantially higher on nesting habitat of shortgrass occupied by prairie dogs compared with agricultural land and shortgrass unoccupied by prairie dogs. The rate of brood movement away from shortgrass with prairie dogs was lower than shortgrass without prairie dogs, but higher than agricultural lands for each year of the study. 4. This study suggests that complex processes influence how different habitats affect brood‐rearing activity of mountain plovers. Even though broods moved off nesting habitat of shortgrass occupied by prairie dogs, this habitat had the highest survival rate and is highly important to mountain plover reproductive success. 5. Synthesis and applications. In order to develop effective conservation strategies, the provision of adequate breeding habitat should include information on patterns of habitat selection for all stages of the breeding cycle, including the nesting and dependent young periods. From a conservation perspective, understanding the habitat use of young birds is critical when population dynamics show great sensitivity to survival of young. Previous studies on mountain plovers have suggested that nest success is similar among shortgrass prairie habitats and agricultural lands. Thus, conservation measures that increase nest success may be ineffective for mountain plovers unless they are accompanied by measures promoting chick survival.

Movements and habitat use by Red-breasted Merganser broods in eastern New Brunswick

Red-breasted Mergansers (Mergus serrator) commonly breed in estuaries, but little is known about their brood-rearing in coastal environments. We measured daily movements and habitat use of radio-marked (n = 17) female Red-breasted Mergansers with broods originating from coastal barrier islands at Kouchibouguac National Park, New Brunswick, Canada from 2002 to 2004. Primary brood movements from nest sites to initial rearing areas were often extensive, averaging 3.5 km (n = 15), since many broods crossed Saint-Louis Lagoon to continental rearing sites. Broods remained mobile throughout the rearing period and there was little difference in daily movements between age class I (days 1–10 post nest exodus), class II (days 11–20), and class III (>20 days) broods. Broods frequented shallow (x̄ = 51 cm, 95% CI: 44–58 cm, n = 191 locations), nearshore (x̄ = 47 m, 95% CI: 33–60 m, n = 157 locations) waters that often supported submergent eel grass (Zostera marina). Broods selected estuarine intertidal regions in Saint-Louis and Kouchibouguac lagoons, as well as wetlands at the mouths of tidal streams. Few broods were found in tidal river and marine habitats. Continental estuarine intertidal, tidal stream, and saltmarsh habitats were preferred by age class I broods whereas estuarine intertidal and subtidal habitats were preferred by age classes II and III. This study highlights the importance of estuarine habitats in lagoons and tidal streams for brood-rearing Red-breasted Mergansers in eastern New Brunswick.

Abundance and Movements of Harlequin Ducks Breeding on Rivers of the Gaspé Peninsula, Québec

In 1996, a study to locate and describe breeding sites, estimate pair densities and document brood movements of Harlequin Ducks (Histrionicus histrionicus) was conducted on selected rivers of the Gaspé Peninsula, Québec. Pair densities on the Port-Daniel, Sainte-Anne and Madeleine River systems were low: 0.32, 0.10 and 0.06 pairs/km, respectively. Six VHF radiotransmitters were implanted in nesting females on the Port-Daniel and Sainte-Anne Rivers. Two successful nests were located on cliff ledges and one unsuccessful nest was located on the ground on an island. These nests represented the first recorded for the eastern North American Harlequin Duck population. Of the marked hens, two successfully hatched ducklings. One was followed for a month until the female was killed by a Great Horned Owl (Bubo virginianus). The brood used a six km stretch of the Sainte-Anne River during that period. The other brood was tracked for two months and concentrated its activities along a three km stretch of the Port-Daniel River. The female was located in coastal waters near Newport on 24 August 1996. Two of the marked females from the Port-Daniel River and one from the Sainte-Anne River migrated to Bonaventure Island, where they likely molted. A female captured on the Port-Daniel River was killed by a Red-tailed Hawk (Buteo jamaicencis) before its nesting status was confirmed. A female from the Port-Daniel River was located at the Sally islands, Maine, on 5 December 1996. The study confirmed the importance of the Gaspé Peninsula Rivers for breeding Harlequin Ducks and the use of adjacent coastal molting sites by postbreeding females. It also established a link with the major Maine wintering area.

King Eider (Somateria Spectabilis) Brood Ecology: Correlates of Duckling Survival

AbstractEvents during duckling growth can influence waterfowl population dynamics. To gain insight into King Eider (Somateria spectabilis) brood ecology, we monitored 111 and 46 individually marked ducklings from broods of 23 and 11 radiomarked King Eiders during 2000 and 2001, respectively. We used capture-mark-resight data to model apparent survival of King Eider ducklings and broods, and multistratum analysis to estimate probabilities of (1) movement among habitats and (2) apparent survival of ducklings that used various habitats. In addition, we recorded length of stay for 7 and 18 radiomarked females with failed nesting attempts during 2000 and 2001, respectively. Complete loss of individual broods accounted for 84% of all duckling mortality (106 of 126 mortalities), with most brood loss (74%; 17 of 23 broods lost) within the first two days after hatch. Estimated apparent survival of ducklings to 24 days of age was 0.10 (95% CI: 0.05 to 0.15). Apparent survival of broods was estimated to be 0.31 (95% CI: 0.13 to 0.50). Our data suggested an interaction between female size and hatch date, whereby larger females whose ducklings also hatched earlier raised more ducklings than either small females or those with ducklings that hatched later. Overland brood movements ≥1 km occurred in both years, and survival was greatest for ducklings on smaller ponds away from the central nesting area at Karrak Lake, Nunavut. Females that experienced nest failure and total brood loss left the study area earlier than females with surviving ducklings.Écologie d'élevage des couvées de Somateria spectabilis : Corrélations avec la survie des canetons

Mallard Brood Movements, Wetland Use, and Duckling Survival During and Following a Prairie Drought

We used radiotelemetry to study mallard (Anas platyrhynchos) brood movements, wetland use, and duckling survival during a major drought (1988–1992) and during the first 2 years of the subsequent wet period (1993–1994) at 4 51-km2 sites in prairie pothole landscapes in eastern North Dakota, USA. About two-thirds of 69 radiomarked mallard broods initiated moves from the nest to water before noon, and all left the nest during daylight. On average, broods used fewer wetlands, but moved greater distances during the dry period than the wet period. Broods of all ages were more likely to make inter-wetland moves during the wet period and probabilities of inter-wetland moves decreased as duckling age increased, especially during the dry period. Brood use of seasonal wetlands nearly doubled from 22% to 43% and use of semi-permanent wetlands declined from 73% to 50% from the dry to the wet period. Eighty-one of 150 radiomarked ducklings died during 1,604 exposure days. We evaluated survival models containing variables related to water conditions, weather, duckling age, and hatch date. Model-averaged risk ratios indicated that, on any given date, radiomarked ducklings were 1.5 (95% CI = 0.8–2.8) times more likely to die when the percentage of seasonal basins containing water (WETSEAS) was ≤18% than when WETSEAS was >40%. An interaction between duckling age and occurrence of rain on the current or 2 previous days indicated that rain effects were pronounced when ducklings were 0–7 days old but negligible when they were 8–30 days old. The TMIN (mean daily minimum temperature on the current and 2 previous days) effects generally were consistent between duckling age classes, and the risk of duckling death increased 9.3% for each 1°C decrease in TMIN across both age classes. Overall, the 30-day survival rate of ducklings equipped with radiotransmitters was about 0.23 lower than the survival rate of those without radiotransmitters. Unmarked ducklings were 7.6 (95% CI = 2.7–21.3) times more likely to die on any given day when WETSEAS was ≤18% than when WETSEAS was >40%. Higher duckling survival and increased use of seasonal wetlands during the wet period suggest that mallard production will benefit from programs that conserve and restore seasonal wetland habitat. Given adverse effects of low temperatures on duckling survival, managers may want to include this stochastic variable in models used to predict annual production of mallards in the Prairie Pothole Region.

Gosling Growth and Survival in Relation to Brood Movements in Greater Snow Geese (Chen Caerulescens Atlantica)

AbstractPost-hatch brood movements to high-quality foraging sites are common in precocial birds but may entail costs for young. We assessed effects of overland movements of broods between the nesting and rearing areas in Greater Snow Geese (Chen caerulescens atlantica) breeding on Bylot Island, Nunavut, Canada, to determine whether these movements affected gosling survival and growth. We monitored 51 radiomarked females over five years to quantify movement distance, movement duration, and gosling survival. Gosling growth was compared over four years using a sample of web-tagged broods recaptured shortly before fledging among adults that (1) nested and reared their young in a dense colony, (2) left the colony and moved ≈30 km to reach the main brood-rearing area, or (3) nested and reared their young in the main brood-rearing area. Brood movements by radio-marked birds were highly variable (2.6-52.5 km, depending on rearing areas used) and fairly rapid (≤6 days after hatch for 72% of the females). Gosling survival was not related to distance moved between nesting and brood-rearing areas. However, gosling growth was influenced by areas used and whether or not they had to move to reach their brood-rearing area. Geese nesting at the main brood-rearing area generally reared heavier and larger goslings than those that moved ≈30 km from the main nesting colony to rear their brood at the main brood-rearing area. On the other hand, goslings leaving the nesting colony after hatch were heavier and larger than those that stayed there throughout brood rearing in one of two years. Although brood movements allow goslings access to high-quality habitats, they entail some costs. Thus, minimizing such movements through nest-site selection should provide a selective advantage by allowing goslings to maximize their growth.Croissance et Survie des Oisons en Relation avec les Déplacements des Familles chez Chen caerulescens atlantica

Habitat use and behaviour of Greater Snow Geese during movements from nesting to brood-rearing areas

Many precocial birds make long-distance movements with their young after hatch to reach the best foraging sites. On Bylot Island, Nunavut, a large number of Greater Snow Goose ( Chen caerulescens atlantica L., 1758) families move 30 km from the main nesting colony (MNC) to reach the main brood-rearing area (MBR) soon after hatch. Geese moving from the MNC to the MBR generally rear lighter and smaller goslings than geese that avoid this movement by both nesting and rearing their brood at the MBR. In this study, we tested the hypotheses that use of low-quality habitats and an increase in the time spent walking at the expense of foraging during movements could explain the reduced growth of goslings in those families. We conducted visual observations to compare habitat use and selection as well as behaviour of geese during brood movements from the MNC to the MBR (i.e., at a transit area) with those of families that had already settled at the MBR. We also conducted aerial tracking to monitor habitat use of 16 radio-marked females during and after brood movements. Streams, wet polygons, and lakes, considered high-quality habitats in terms of feeding opportunities and predator refuges, were preferred, while upland, a low-quality habitat, was avoided at both the transit area and the MBR. However, broods were found in the upland habitat more often during movements than once settled on a rearing site. The behaviour of unmarked geese at the transit site did not differ from that of geese at the MBR. We suggest that reduced food intake in low-quality habitats during movements, but not the increase in time spent walking, may explain the reduction in growth observed at fledging in goslings moving from the MNC to the MBR.

Spatial differences in breeding success in the pied avocet Recurvirostra avosetta: effects of habitat on hatching success and chick survival

I studied the breeding biology of pied avocets Recurvirostra avosetta in natural habitats (alkaline lakes), and in semi‐natural sites (dry fishpond, reconstructed wetlands) in Hungary to relate habitat selection patterns to spatial and temporal variation in breeding success. Colonies were initiated earlier in semi‐natural sites than in natural habitats, and earlier on islands than on the mainland. Hatching success was higher on islands than on the mainland, in semi‐natural sites than in natural habitats, in colonies of at least 15 pairs than in smaller colonies, and for nests initiated earlier than later within a colony. Fledging success was higher in the wet years (1999–2000) than in the dry year (1998), decreased strongly by season in both habitats and increased with average daily temperature in the first week post‐hatch in 1999–2000. Most pairs hatching young in semi‐natural sites attempted to lead their chicks to feeding areas in natural habitats, whereas no such movement occurred in the opposite direction. Chick mortality due to predation was high during brood movements and only 23% of the pairs moving their young produced fledglings, compared to 43% for pairs remaining in semi‐natural sites and 68% for pairs hatching and rearing young in natural habitats (total n=192 broods). These results suggest that semi‐natural sites were more suitable for nesting, whereas natural habitats were more suitable for chick‐rearing. The opposing trends in habitat‐related breeding success between nesting and chick‐rearing suggest sub‐optimal habitat selection by Pied Avocets due to an incorrect assessment of the potential for successful reproduction of semi‐natural sites, which may thus function as ecological traps.

Brood Movements of Eastern Prairie Population Canada Geese: Potential Influence of Light Goose Abundance

During the summers of 2000–2002, we used radio telemetry to document Eastern Prairie Population (EPP) Canada goose (Branta canadensis interior) brood movements and use of brood-rearing habitat. We compared these data with similar data collected in 1976–1978 (Didiuk 1979), prior to a significant increase in the size of the midcontinent light goose (lesser snow geese [Chen caerulescens] and Ross's geese [C. rossii]) population and consequent habitat alteration near Cape Churchill, Manitoba. Since the late 1970s, use of traditional EPP Canada goose brood-rearing areas by light geese has increased significantly near Cape Churchill, and the density of nesting EPP Canada geese has declined. Alteration of brood-rearing habitat has been hypothesized as a cause of the decline in EPP breeding density, as natal dispersal to more distant brood-rearing areas may influence future recruitment into the local breeding population. In 1976–1978, 20 (95%) of 21 radio-marked broods nesting in beach ridge/sedge meadow habitat moved to salt marsh brood-rearing areas; however, only 5 (19%) of 27 Canada geese, nesting in the same habitat, made initial movements to these traditional salt marsh brood-rearing areas in 2000–2002. In 2000–2002, 30 (75%) of 40 geese with broods made initial movements to beach ridge/sedge meadow habitat—10 of these broods eventually moved to salt-marsh habitats later in the brood-rearing period (χ date = 22 days postmedian hatch). Mean brood home range size from 2001–2002 in coastal and inland habitats nearly doubled compared to the mean brood home range size during 1976–1978. Eastern Prairie Population Canada geese currently use brood-rearing habitat other than the coastal salt marshes they used prior to habitat alteration resulting from foraging by light geese. A shift in the use of brood-rearing habitat could potentially reduce nest densities on the study area if first-time breeders nest closer to distant brood-rearing areas. The impact of alternative brood-rearing habitat on gosling growth and survival for EPP geese is unknown, but foraging in poorer quality brood-rearing habitat may also contribute to the observed decline in nesting density.

GOSLING GROWTH AND SURVIVAL IN RELATION TO BROOD MOVEMENTS IN GREATER SNOW GEESE (CHEN CAERULESCENS ATLANTICA)

Post-hatch brood movements to high-quality foraging sites are common in precocial birds but may entail costs for young. We assessed effects of overland movements of broods between the nesting and rearing areas in Greater Snow Geese (Chen caerulescens atlantica) breeding on Bylot Island, Nunavut, Canada, to determine whether these movements affected gosling survival and growth. We monitored 51 radiomarked females over five years to quantify movement distance, movement duration, and gosling survival. Gosling growth was compared over four years using a sample of web-tagged broods recaptured shortly before fledging among adults that (1) nested and reared their young in a dense colony, (2) left the colony and moved ≈30 km to reach the main brood-rearing area, or (3) nested and reared their young in the main brood-rearing area. Brood movements by radio-marked birds were highly variable (2.6-52.5 km, depending on rearing areas used) and fairly rapid (≤6 days after hatch for 72% of the females). Gosling survival was not related to distance moved between nesting and brood-rearing areas. However, gosling growth was influenced by areas used and whether or not they had to move to reach their brood-rearing area. Geese nesting at the main brood-rearing area generally reared heavier and larger goslings than those that moved ≈30 km from the main nesting colony to rear their brood at the main brood-rearing area. On the other hand, goslings leaving the nesting colony after hatch were heavier and larger than those that stayed there throughout brood rearing in one of two years. Although brood movements allow goslings access to high-quality habitats, they entail some costs. Thus, minimizing such movements through nest-site selection should provide a selective advantage by allowing goslings to maximize their growth. Croissance et Survie des Oisons en Relation avec les Déplacements des Familles chez Chen caerulescens atlantica

SURVIVAL OF WESTERN SANDPIPER BROODS ON THE YUKON-KUSKOKWIM DELTA, ALASKA

Abstract The rate of chick growth in high-latitude breeding shorebirds is rapid, but little is known about the effect of chick mass, growth, and brood movements on subsequent brood survival. To address these topics, we monitored chick growth patterns, daily brood movements, and survival of Western Sandpipers (Calidris mauri) on the Yukon-Kuskokwim Delta, Alaska. We assessed the effect of chick age, mass, and hatch date on brood survival using Program MARK. We mapped brood locations daily, and compared brood movement patterns between successful and unsuccessful broods. Younger chicks survived at lower rates and moved shorter distances than older chicks. The overall probability of one or more chicks from a brood surviving to 15 days of age was 0.73 ± 0.05 SE. Brood survival declined seasonally, and broods with heavier chicks survived at higher rates than those with lighter chicks. On average, successful broods fledged 1.7 ± 0.1 SE chicks. Rate of chick growth was intermediate between those of high arctic an...