Hatch Date Research Articles

Recruitment dynamics and fishery characteristics of juvenile goatfishes Mulloidichthys spp. in Hawai'i.

The most common goatfishes in Hawai'i, Mulloidichthys flavolineatus and M. vanicolensis, comprise a unique resource due to their cultural, ecological and biological significance. These species exhibit pulse-type recruitment to nearshore areas during the summer months. Such pulses of juvenile fishes provide prey for pelagic and nearshore fishes and support a popular directed fishery. However, limited scientific information exists on juvenile stages of these fishes, known locally as oama, despite their contribution to coastal ecology and the extensive nearshore fisheries. Here we resolve growth rates, habitat preferences, hatching dates, size and age structure, as well as fishing catch rates based on new recruits in 2014 and 2015. We sampled 257 M. flavolineatus and 204 M. vanicolensis to compare ecological and fisheries characteristics between species and years. Both show strong habitat segregation, with M. vanicolensis found almost exclusively on hard and M. flavolineatus on soft substrates. Oama recruited in anomalously high numbers in 2014, a trend reflected in a higher catch per unit effort. In contrast, 2015 recruits grew faster, were heavier on average and hatched later than during 2014. Both species have calculated hatch dates in March to July, with M. vanicolensis hatching earlier, recruiting earlier and being consistently larger than M. flavolineatus. This baseline information regarding recruitment and early life-history characteristics can enhance management for other data-limited species that comprise a substantial component of nearshore fisheries in Hawai'i.

Managed spring runoff to improve nursery floodplain habitat for endangered Rio Grande silvery minnow

AbstractWater managers in New Mexico, USA, stored water in El Vado Reservoir and coordinated releases into the Chama River that augmented the runoff of the Rio Grande, resulting in a discharge >1,500 ft3/s (42.5 m3/s) for 35 days (May 17 to June 20, 2016) at Albuquerque. The managed runoff inundated over 400 ha of previously restored floodplains in the Middle Rio Grande, thereby providing spawning and nursery habitat for the endangered Rio Grande silvery minnow (Hybognathus amarus, RGSM). Spawning began April 9 at annual cumulative degree‐days of 717, during daily increases in discharge of 200–300 ft3/s (5.7–8.5 m3/s), and hatch dates were normally distributed over 53 days (April 11 to June 3). RGSM were 73% of larvae collected in six restored floodplain sites and found in shallow water (mean = 19.6 cm), low velocity (mean = 3.9 cm/s), near vegetative cover, and with 75% within 1 m of the water's edge. Declining proportions of early to late larval phases and a near absence of juveniles indicate a gradual departure from floodplains as postflexion mesolarvae and metalarvae 14–22 days post hatch (dph), with most leaving by the juvenile stage 40 dph. The annual RGSM October census showed an increase of 0.16 to 7.20 fish/100 m2 from 2015 to 2016, indicating that the managed runoff resulted in a positive population response. This study showed that constructing floodplains and managing river and reservoir operations to inundate those floodplains during and after RGSM spawning can provide nursery habitat that improves reproductive success and recruitment.

Understanding the life histories of amphidromous fish by integrating otolith‐derived growth reconstructions, post‐larval migrations and reproductive traits

Abstract Amphidromy is the most prevalent type of diadromous migration. Despite this, the conservation and management of amphidromous species is exceptionally challenging because this life history type, with larval development in a pelagic habitat (usually marine) and adult development in fresh water, is poorly resolved. The chronological properties of otoliths, together with a spatial and temporal analysis of post‐larval migration traits and adult reproductive traits, were used to reconstruct the life history of a widespread, yet declining amphidromous galaxiid, Galaxias maculatus, and to explore relationships between marine and freshwater life phases. A wide range of post‐larval migration traits were observed over the peak migratory period. Post‐larvae were smaller and younger at inward migration late in the migration season (November) and were derived from winter spawning events. Earlier migrants (September) were larger, older and derived from autumn spawning events. Age estimates confirmed that G. maculatus is largely an annual species, but back‐calculated hatch dates showed that spawning times are more extensive than previously known. Growth reconstructions revealed that winter‐hatched larvae were faster growing during marine and freshwater life and attained sexual maturity at a younger age than autumn‐hatched fish. However, no differences in body size or reproductive investment were detected between autumn‐ and winter‐hatched larvae. The first 50 days of marine growth were inter‐dependent, indicating that early larval growth may be the critical link to understanding intra‐ and inter‐annual recruitment variations of inward migrating post‐larvae. Furthermore, growth after 60 days of larval life propagated through to adult freshwater development, highlighting linkages between late marine and adult freshwater life. This study highlights the value of studying the marine and freshwater life phases of amphidromous species in tandem. This interconnected understanding must ultimately be achieved for the conservation and management of species with this poorly understood life history type.

Canada Goose Gosling Mortality During Prefledging and Early Migration on Akimiski Island, Nunavut

Abstract Mortality rates for precocial avian species are highest during their first year of life. For harvested species, including waterfowl, it is particularly difficult to determine causes of mortality using standard mark–recapture techniques. The timing and cause of nonhunting mortality is difficult for researchers to distinguish, and therefore, difficult to incorporate into management decisions. We marked flightless Canada goose Branta canadensis interior goslings with radio transmitters to determine the timing of mortality prior to harvest during the fall migration. We tracked survival of 206 goslings for 2 mo from an average of 50 d of age to just prior to the fall migration departure from the breeding grounds in 1999 and 2000. The most parsimonious model from a set of candidate models describing probability of survival showed clear differences between years and suggested that survival was affected by gosling size (largest survived better) and hatch timing disparity. We indexed hatch timing disparity by measuring the difference between gosling hatch date and the date of the estimated peak in forage quality as determined by the normalized difference vegetation index. The latest hatched goslings presumably had the lowest quality forage available to them. Both size and hatch timing disparity concur with a mortality cause that is most likely from complications due to malnutrition. The estimated survival probability of goslings to 51 d post marking was 0.31 (95% confidence limit = 0.22 to 0.44) in 1999 and 0.69 (95% confidence limit = 0.57 to 0.83) in 2000. Managers can make better informed decisions concerning the utility of harvest regulation in the conservation of juvenile Canada geese by better understanding the timing, causes, and annual variation of their mortality.

Trends in Sandeel Growth and Abundance off the East Coast of Scotland

Sandeels Ammodytes marinus are a crucial forage fish species in the North Sea, transferring zooplankton energy to higher trophic levels. However, there has been a sustained decline in sandeel abundance in the northwestern North Sea since 2000. Here we use field data to analyze year-to-year changes in A. marinus growth rate between 1997 and 2009 and assess whether variation in growth rate corresponded with variation in abundance. The signature of the reduction in abundance between 2000 and 2009 was a decline in age 1 sandeels, while no other age class declined. Analysis of age-length data showed that the decline in abundance coincided with a period of low growth. Growth performance indexes were correlated with zooplankton and phytoplankton biomass but not temperature. Further, we observed a significant correlation between larval growth rate and 0-group sandeel length during a period when hatch dates were relatively fixed; suggesting recent changes in length were influenced by food availability.

Potential Effect of Migration Strategy on Pollutant Occurrence in Eggs of Arctic Breeding Barnacle Geese ( Branta leucopsis).

Arctic-breeding geese acquire resources for egg production from overwintering grounds, spring stopover sites and breeding grounds, where pollutant exposure may differ. We investigated the effect of migration strategy on pollutant occurrence of lipophilic polychlorinated biphenyls (PCBs) and protein-associated poly- and perfluoroalkyl substances (PFASs) and mercury (Hg) in eggs of herbivorous barnacle geese ( Branta leucopsis) from an island colony on Svalbard. Stable isotopes (δ13C and δ15N) in eggs and vegetation collected along the migration route were similar. Pollutant concentrations in eggs were low, reflecting their terrestrial diet (∑PCB = 1.23 ± 0.80 ng/g ww; ∑PFAS = 1.21 ± 2.97 ng/g ww; Hg = 20.17 ± 7.52 ng/g dw). PCB concentrations in eggs increased with later hatch date, independent of lipid content which also increased over time. Some females may remobilize and transfer more PCBs to their eggs, by delaying migration several weeks, relying on more polluted and stored resources, or being in poor body condition when arriving at the breeding grounds. PFAS and Hg occurrence in eggs did not change throughout the breeding season, suggesting migration has a greater effect on lipophilic pollutants. Pollutant exposure during offspring production in arctic-breeding migrants may result in different profiles, with effects becoming more apparent with increasing trophic levels.

Temperature—Not Flow—Predicts Native Fish Reproduction with Implications for Climate Change

AbstractHabitat alterations and introduction of nonnative fishes reduced the distributions of the Flannelmouth Sucker Catostomus latipinnis, Bluehead Sucker C. discobolus, and Roundtail Chub Gila robusta to less than 50% of their historical ranges. Climate change models generally predict decreased streamflows and increased water temperatures that may further affect these species. Understanding the effects of flow and water temperature on their life histories should lead to better assessments of climate change impacts on extant populations and more informed management for species conservation. Basinwide larval fish sampling and hatch dates derived from otolith daily increment counts showed that water temperature was the dominant environmental factor cueing reproduction in the upper White River basin, Colorado. Reproduction for all three species began in spring, occurring first at warmer, lower‐elevation, downstream locations and progressing upriver to higher elevations as water temperatures increased. Warmer water temperatures in tributaries initiated earlier reproductive activity compared to adjacent cooler main‐stem habitat. Presence of larvae in samples and estimated hatch dates demonstrated a distinct, predictable upstream progression of reproduction associated with warming water and clear upstream limits to reproduction for all three species. Larval presence and hatching dates revealed earlier reproductive activity in 2012 than in 2013, driven by lower flow and earlier stream warming. A regression model predicted stream temperature during fish spawning seasons under different climate change scenarios and showed expanded upstream limits of thermally suitable reproductive habitat and earlier reproduction for our study species. The long‐term implications of climate change are unknown, but managers should strive to perpetuate the valuable and relatively pristine native fish community in the upper White River drainage as a vestige of those that formerly existed throughout the Colorado River basin.

Comparative age and growth of Uroteuthis chinensis and Uroteuthis edulis from China Seas based on statolith

To determine the age and growth of Uroteuthis chinensis and U. edulis, growth increments of the lateral dome of the statolith were used in the present study. Specimens of the two species caught in the South China Sea (SCS) and East China Sea (ECS) were used to compare the age and growth differences between sexes. In the present study, we found the two species have similar lifespans of less than 200 days. We also found that there were significant differences in the relationships between mantle length and body weight for two species and for both sexes in the same species. The back-calculated hatching date for the two species was similar, i.e. October to January for specimens caught in spring, and March to June for specimens caught in summer (U. edulis) or autumn (U. chinensis). Exponential and logistic growth curves were fitted to build the age and mantle length relationship. Both growth curves showed that U. chinensis has a larger mantle length than U. edulis at the same age. The results of the growth rates also showed that U. chinensis grows faster than U. edulis. However, there are discrepancies between previous studies and the present study on the lifespan of the two species. Also, the sample size of the present study is small especially for U. edulis. Hence, future studies should be conducted to validate the daily periodicity of growth increment in the regions of statolith (except for the lateral dome which has been validated) and the sample size should be increased for age and growth studies.

Timing of Sandeel Spawning and Hatching Off the East Coast of Scotland

The lesser sandeel, Ammodytes marinus, is a key forage fish species in the North Sea. Mean lengths and abundances of sandeels have declined steeply since the 1990’s and these are associated with declining breeding success of various seabird species on the east coast of Scotland, especially kittiwakes. The declining lengths have led to a mismatch between the peak in food demand arising from chick rearing, and the appearance of appropriately sized young sandeels in the foraging areas of the birds. A 10-year time series of sandeel larval samples between 2000 and 2009 offer a rare opportunity to analyze trends in spawning and hatch dates and determine whether they contributed to changes in mean lengths. By analyzing the abundance, length, and age distributions of sandeel larvae we were able to determine the temporal distribution of hatching rates each year, and back-track to the likely spawning dates of the sandeels. Estimated spawning dates showed no evidence of correlation with environmental cues such as tidal or lunar phases. However, hatch end dates varied by 20 days over the 10-year period and were correlated with the date of the seasonal minimum of sea bottom temperature. We show a significant decline between growth rate and 0-group length between 2000 and 2009, and suggest that changes in food quality and availability, rather than shifts in hatch dates, are likely to be responsible for current declines in the availability of sandeels to seabirds.

Local egg production and larval losses to advection contribute to interannual and long-term variability of American lobster (Homarus americanus) settlement intensity

American lobster (Homarus americanus) egg production and settlement intensity were examined over a 19-year period (1995–2013) in the Gulf of St. Lawrence at the Magdalen Islands (MI), where the population is spatially isolated during the benthic phase. Settlement and hatch dates by year were back-calculated from observed young-of-the-year size structure and juvenile and larval growth models. Drift of locally released larvae, from stage I to the end of stage III, was simulated using an ocean circulation model. Settlement intensity was related positively to egg production and negatively to drift distance. There was a strong positive trend in settlement intensity explained largely by increasing egg production, as well as by declining larval duration and drift distance. In the last years of the study, settlement intensity may have been limited by nursery saturation. The results suggest that demographic connectivity through larval drift is highly dynamic in time and that it declined during our study period. The demographic dependence of the MI lobster population on other populations in the Gulf of St. Lawrence is probably low.

Linking warming effects on phenology, demography, and range expansion in a migratory bird population.

Phenological changes in response to climate change have been recorded in many taxa, but the population‐level consequences of these changes are largely unknown. If phenological change influences demography, it may underpin the changes in range size and distribution that have been associated with climate change in many species. Over the last century, Icelandic black‐tailed godwits (Limosa limosa islandica) have increased 10‐fold in numbers, and their breeding range has expanded throughout lowland Iceland, but the environmental and demographic drivers of this expansion remain unknown. Here, we explore the potential for climate‐driven shifts in phenology to influence demography and range expansion. In warmer springs, Icelandic black‐tailed godwits lay their clutches earlier, resulting in advances in hatching dates in those years. Early hatching is beneficial as population‐wide tracking of marked individuals shows that chick recruitment to the adult population is greater for early hatched individuals. Throughout the last century, this population has expanded into progressively colder breeding areas in which hatch dates are later, but temperatures have increased throughout Iceland since the 1960s. Using these established relationships between temperature, hatching dates and recruitment, we show that these warming trends have the potential to have fueled substantial increases in recruitment throughout Iceland, and thus to have contributed to local population growth and expansion across the breeding range. The demographic consequences of temperature‐mediated phenological changes, such as the advances in lay dates and increased recruitment associated with early hatching reported here, may therefore be key processes in driving population size and range changes in response to climate change.

No effects of asynchrony between hatching and peak food availability on chick growth in Semipalmated Plovers (Charadrius semipalmatus) near Churchill, Manitoba

Birds rely on consistent patterns of food availability on their breeding grounds to successfully complete their breeding cycle. Due to ongoing warming of the sub-Arctic, there is potential for a mismatch between the peak in available invertebrate biomass and the peak in food demand for shorebird chicks. During the summers of 2010 and 2011, we investigated the relationship between temperature and benthic and terrestrial invertebrate biomass, measured using three sampling techniques in Churchill, Manitoba. We also investigated the relationship between timing of breeding of Semipalmated Plovers (Charadrius semipalmatus) and timing of peaks in invertebrate biomass. In 2011, chick growth rates were also measured to examine whether hatching in synchrony with the peak in invertebrate biomass during the brood rearing period affected growth rates. In 2010, emergent and core invertebrate biomass were negatively related to soil degree days, whereas in 2011, core biomass increased with soil degree days and pitfall biomass increased with air temperature. Total invertebrate biomass (summed over trap types) peaked from 25 to 31 days before the median chick hatch date in 2010 and 10 days after the median chick hatch date in 2011. In 2011 we did not detect any effects of asynchrony on the growth of Semipalmated Plover chicks. These results may indicate that food resources in their environment remain adequate throughout the breeding season, despite inter-annual fluctuations in the timing of invertebrate peaks.

Breeding synchrony and predator specialization: A test of the predator swamping hypothesis in seabirds.

Reproductive synchrony is a widespread phenomenon that is predicted to be adaptive for prey with specialist predators but not for those with generalist ones. I tested this prediction in three polar seabird species characterized by different levels of predator specialization. In the Antarctic petrel, for which the only predator was highly specialized, hatching dates were highly synchronous and chicks that hatched close to the mean hatching date had a higher survival. In black‐legged kittiwakes and Brünnich's guillemots, whose predators were generalists, breeding was less synchronous and there was no fitness advantage in hatching close to the mean. This study emphasizes the potential importance of the relative timing of reproduction for individual fitness and supports the hypothesis that the adaptive value of breeding synchrony depends on the predator functional response.

Role of freshwater floodplain-tidal slough complex in the persistence of the endangered delta smelt.

Seasonal floodplain wetland is one of the most variable and diverse habitats found in coastal ecosystems, yet it is also one of the most highly altered by humans. The Yolo Bypass, the primary floodplain of the Sacramento River in California’s Central Valley, USA, has been shown to provide various benefits to native fishes when inundated. However, the Yolo Bypass exists as a tidal dead-end slough during dry periods and its value to native fishes has been less studied in this state. During the recent drought (2012–2016), we found higher abundance of the endangered Delta Smelt (Hypomesus transpacificus), than the previous 14 years of fish monitoring within the Yolo Bypass. Meanwhile, Delta Smelt abundance elsewhere in the estuary was at record lows during this time. To determine the value of the Yolo Bypass as a nursery habitat for Delta Smelt, we compared growth, hatch dates, and diets of juvenile Delta Smelt collected within the Yolo Bypass with fish collected among other putative nursery habitats in the San Francisco Estuary between 2010 and 2016. Our results indicated that when compared to other areas of the estuary, fish in the Yolo Bypass spawned earlier, and offspring experienced both higher quality feeding conditions and growth rates. The occurrence of healthy juvenile Delta Smelt in the Yolo Bypass suggested that the region may have acted as a refuge for the species during the drought years of 2012–2016. However, our results also demonstrated that no single region provided the best rearing habitat for juvenile Delta Smelt. It will likely require a mosaic of habitats that incorporates floodplain-tidal sloughs in order to promote the resilience of this declining estuarine fish species.

Timing manipulations reveal the lack of a causal link across timing of annual-cycle stages in a long-distance migrant.

Organisms need to time their annual-cycle stages, like breeding and migration, to occur at the right time of the year. Climate change has shifted the timing of annual-cycle stages at different rates, thereby tightening or lifting time constraints of these annual-cycle stages, a rarely studied consequence of climate change. The degree to which these constraints are affected by climate change depends on whether consecutive stages are causally linked (scenario I) or whether the timing of each stage is independent of other stages (scenario II). Under scenario I, a change in timing in one stage has knock-on timing effects on subsequent stages, whereas under scenario II, a shift in the timing of one stage affects the degree of overlap with previous and subsequent stages. To test this, we combined field manipulations, captivity measurements and geolocation data. We advanced and delayed hatching dates in pied flycatchers (Ficedula hypoleuca) and measured how the timing of subsequent stages (male moult and migration) were affected. There was no causal effect of manipulated hatching dates on the onset of moult and departure to Africa. Thus, advancing hatching dates reduced the male moult-breeding overlap with no effect on the moult-migration interval. Interestingly, the wintering location of delayed males was more westwards, suggesting that delaying the termination of breeding carries over to winter location. Because we found no causal linkage of the timing of annual-cycle stages, climate change could shift these stages at different rates, with the risk that the time available for some becomes so short that this will have major fitness consequences.

Age estimation of striped marlin (Kajikia audax) in the eastern North Pacific using otolith microincrements and fin spine sections

The age of striped marlin (Kajikia audax) in days and years (daily and yearly ages) were estimated by counts of otolith microincrements (n=25) and dorsal fin spine annuli (n=175) using specimens caught in the tropical eastern North Pacific between September and November 2004. Daily ages of small striped marlin (87.0–145.5cm lower jaw–fork length) were estimated to range from 81 to 239 days, which indicates that the species in the area grow, on average, to over 100cm within 4 months. Back-calculated hatch dates were estimated to be from March to July; this period is earlier than the known spawning season in a slightly more northern area. Approximately 20% of these year-0 striped marlin had one or more growth bands in the sectioned spine. They were thought to be false annual growth bands and excluded from yearly age estimation. The estimated yearly age of 175 individuals (87.0–228.4cm) ranged from 0 to 5 and was dominated by ages-0 to 3 (>90%). Age composition was different among three subregions in the eastern North Pacific.

Effect of Immuguard immune stimulator on broilers; productivity and quality of meat

The authors highlight that broiler poultry is considered to be one of the most profitable and promising sectors of agriculture. At the same time, industrial technologies experience unsolved problems, such as death of young poultry in the first weeks of life due to the lack of resistible immune system, which is formed by the end of the third week. In this regard, development and application of immune stimulating specimens is a promising direction for stimulation and maintenance of natural poultry resistance and improve its economic parameters. The specimens used should not affect the quality and products safety. The example of such specimen is ImmuGuard; it was tested in the experimental vivarium conditions at the Department of Veterinary and Sanitary Expertise of Livestock Products And Hygiene of Agricultural Animals at the Institute of Veterinary Medicine And Biotechnology of Omsk State Agrarian University. The researchers arranged three experimental groups from Ross broilers on the basis of similarity. 1st experimental group received the specimen dosed 150; second group of broilers -250 g / t of water during 18 days from the date of hatching, and the 3rd group was arranged as a control one. Growth and weight parameters were determined by individual weighing of poultry every seven days. The quality of broilers’ meat was assessed by means of conventional methods used in veterinary and sanitary assessment of poultry meat. The experience showed a positive effect of the specimen on live weight gain of poultry: the authors observed body weight of broilers aged 42 days from first experimental group was 4.12 higher; broilers from the 2nd group 1.39% in comparison with the control group. The authors highlight a significant increase in the average daily growth: the 1st group showed the growth on 32.21% from the 22nd to the 35th day in respect to the control parameters. Organoleptic, physico-chemical and microbiological parameters of meat of all groups conformed to GOST 31470-2012 and SanPiN 2.3.2.1078-01 standards.

Phenology of hatching and food in low Arctic passerines and shorebirds: is there a mismatch?

The warming climate is driving earlier spring snow melt and longer growing seasons in tundra regions of northwestern North America, thereby changing the timing of ecological processes. On Herschel Island, Yukon, Canada, we investigated changes in the migratory bird community, and the potential for phenological mismatch of egg hatching with the pulses in abundance of arthropod prey on which young birds depend for growth. We found an apparent reduction in abundance or loss of some species dependent on freshwater ponds or sparsely vegetated upland tundra. Tracking hatch dates of passerines and shorebirds along with the changes in biomass of mobile life history stages of arthropods (principally Araneae, Tipulidae, Carabidae, Muscidae, Chironomidae, Mycetophilidae, and Ichneumonidae), we found no evidence for phenological mismatch in the 2007–2009 time period. Most nests hatched, and the period of most rapid chick growth occurred, in advance of the highest availability of arthropod biomass. Shorebirds hatched significantly later than passerines, less in advance of the peak abundances of arthropods. They are most at risk of future mismatch, given likely trend to earlier onset of arthropod availability and longer migration routes. Herschel Island is a well-studied site warranting further monitoring to assess changes in the Arctic tundra ecosystem.

Small changes in timing of breeding among subarctic passerines over a 32‐year period

Many bird populations in temperate regions have advanced their timing of breeding in response to a warming climate in recent decades. However, long‐term trends in temperature differ geographically and between seasons, and so do responses of local breeding populations. Data on breeding bird phenology from subarctic and arctic passerine populations are scarce, and relatively little data has been recorded in open‐nesting species. We investigated the timing of breeding and its relationship to spring temperature of 14 mainly open‐nesting passerine species in subarctic Swedish Lapland over a period of 32 years (1984–2015). We estimated timing of breeding from the progress of post‐juvenile moult in mist‐netted birds, a new method exploring the fact that the progress of post‐juvenile moult correlates with age. Although there was a numerical tendency for earlier breeding in most species (on average −0.09 days/year), changes were statistically significant in only three species (by −0.16 to −0.23 days/year). These figures are relatively low compared with what has been found in other long‐term studies but are similar to a few other studies in subarctic areas. Generally, annual hatching dates were negatively correlated with mean temperature in May. This correlation was stronger in long‐distance than in short‐distance migrants. Although annual temperatures at high northern latitudes have increased over recent decades, there was no long‐term increase in mean temperature in May over the study period at this subarctic site. This is probably the main reason why there were only small long‐term changes in hatching dates.

FITNESS CONSEQUENCES OF PARENTAL BEHAVIOR IN RELATION TO OFFSPRING NUMBER IN A PRECOCIAL SPECIES - THE LESSER SNOW GOOSE

We investigated the relationship between parental behavior and brood size, and the consequences of this relationship in terms of parental fitness (timing of molt and body mass at onset of molt in same year as breeding, and probability of return, timing of breeding, and clutch size in following year) in the precocial Lesser Snow Goose (Chen caerulescens caerulescens) at La Perouse Bay, Manitoba. The percentage of time parent birds spent feeding decreased with increasing brood size, from greater than 90% for pairs without off-spring to less than 80% for broods of seven and eight. The number of vigilant (head-up) postures per minute by parental birds increased up to brood size five and then decreased. Parental females also spent significantly less total time feeding and more time in alert behavior as brood size increased from one to five goslings. The relationship between parental behavior and brood size remained significant for small brood sizes even if pairs without goslings were excluded (range one to five goslings), and this relationship was independent of female age. Males (but not females) rearing larger broods molted later than those with smaller broods, although only by one to two days. This was directly related to rearing of offspring; in both sexes, birds that hatched four or more goslings and subsequently lost one or more goslings during brood-rearing molted significantly earlier than birds rearing all of their hatched goslings. There was no relationship, in either sex, between number of goslings reared and the adult mass five to six weeks posthatch (molt) in the same year, or probability of return or timing of breeding (laying date or hatch date) in the following year. Partners of males that reared the largest number of goslings laid significantly larger clutch sizes the following year, suggesting that these were ''better-quality'' pairs. Over the range of naturally observed brood sizes, the effect of increasing brood size on parental behavior does not appear to be associated with any negative effects on residual parental reproductive effort or fitness in this species.