Breeding biology of the thin-billed prion<Emphasis Type="Italic"> Pachyptila belcheri</Emphasis> at New Island,Falkland Islands: egg desertion,breeding success and chick provisioning in the poor season 2002/2003

We present data on breeding success, chick growth and chick feeding in thin-billed prions, Pachyptila belcheri, at New Island, Falkland Islands, in the breeding season 2002/2003. As in many populations of seabirds in the region, the overall breeding success was very low. This was mainly caused by low rate of observed burrow occupancy (60%) and hatching (57%) of thin-billed prions, while chick survival was closer to normal. Sixty-eight percent of the chicks survived to fledging. In total, a chick was successfully reared in 23% of the nests or from 38% of recorded eggs. The failed eggs were found to be incubated for 30 days, on average. The time of egg desertion coincided with the time of desertion of other seabirds at New Island, with a period of high sea-surface temperatures and low catch rates by the commercial fisheries. We describe chick growth and use repeated weighings, corrected for metabolic loss, to estimate meal sizes. Chicks were fed a mean 39.2 g in 77% of the nights. We discuss possible reasons for the observed extremely low hatching success, and compare with the breeding success of other seabirds at the Falkland Islands.     

Breeding systems of New Zealand Snipe Coenocorypha aucklandica and Chatham Island Snipe C. pusilla; are they food limited?

New Zealand Snipe Coenocorypha aucklandica were studied over six breeding seasons on the Snares Islands. The study area (7.5 ha) held about 20 pairs at a density of 3.2 ± O.5 pairs/ha, plus 5 to 25 nonterritorial birds. Most matings were monogamous but simultaneous polygyny was recorded in one territory (by two different males) in four consecutive seasons. Males courtship fed females before egg-laying. The typical clutch was two eggs, laid three days apart. Incubation was shared equally by the sexes in monogamous pairs and took 22 days. Some females with polygynous mates attempted to incubate unaided, which took about 38 days. Broods were split at hatching, with the male caring for the first chick to leave the nest. Chicks were fed by adults for at least 41 days, and did not become independent until about 65 days old. Growth rates were slow compared to Common Snipe Gallinago gallinago and full plumage took about 54 days to attain. No pairs were double-brooded but 43% of pairs that failed during incubation or early chick-rearing renested together. Some breeders of both sexes who had lost their dependent chick bred a second time with a new mate while their first mate continued rearing the surviving chick (sequential polygyny and polyandry). Hatching success was 80%, and fledging success was 48%. Each pair produced, on average, O.6 fledglings per year. Chatham Island Snipe C. pusilla were studied on Rangatira Island during the 1983–84 breeding season. Breeding density was about 5.6 pairs/ha. The breeding system was very similar to that for C. aucklandica but chicks became independent at about 41 days old. Hatching success was 89%. Compared to Common Snipe, Coenocorypha snipes occurred at high densities, had courtship feeding, large eggs, a long interegy interval, a small clutch, shared incubation and a long incubation period. Nest desertion rates were high, but overall hatching success was also high, chick growth rates were slow, there was a long period of chick dependence and a long relaying interval following nest failure or chick loss. Survival rates of both adults and chicks were high. These differences are attributed to the absence of predation, and to intense intraspecific competition for food in a stable environment.     

4. UNUSUAL EXPERIENCES WITH BIRDS

Earlé, R. A. 1989. Breeding biology of the Redbreasted Swallow Hirundo semirufa. Ostrich 60: 13–21.

The two races of the Redbreasted Swallow Hirundo semirufa seem to have separate breeding seasons with the northern race H. s. gordoni breeding April-July, while most records for the nominate race fall in October-February. All nests studied were in concrete culverts less than 1 m high. Eggs laid in second clutches by individual females weighed significantly less than eggs laid in first clutches. Eggs hatched on average 16,2 days after incubation started or 18–21 days after the eggs were laid. Only females incubated. Chicks fledged 23–25 days after hatching and reached a maximum body mass of about 31,5 g on day 18 before a steady decline in mass until fledging. Most nesting failures resulted from infertile eggs or starvation of young in the nest (16,2% of all young starved). Overall breeding success was 60,6%. In all, 81,8% of first clutches produced fledglings but only 44,4% of second clutches. Over a three year period 4,9 young were produced per pair breeding in the area (1,6 young/pair/breeding season).     

1. A CENSUS AND STUDY OF BIRDS IN ALBANY OPEN THORNBUSHVELD

Williams, A. J. &; Cooper, J. 1983. The Crowned Cormorant: breeding biology, diet, and offspring reduction strategy. Ostrich 54:213-219.

Crowned Cormorants Phalacrocorax coronatus were studied at Dassen and Marcus Islands. The most frequent clutch was three eggs. Egg size varied within clutches with first-laid eggs being largest and heaviest and subsequent eggs progressively smaller and lighter, The mean laying interval was 2,2 days, the mean laying-to-hatching interval was 23,0 days, and the hatching interval was one day. The normal incubation period was 22.4 days. The weight of hatchings was related to the position of the originating egg in the laying sequence. Chicks were fed within 24 h of hatching. Chick development is described over the first 35 days. One chick could fly at 35 days. Hatching success was 48,2%. Hatching success was greatest in second-laid eggs, least in last-laid eggs. The mean number of chicks hatched at a nest was two. Mean diving time was 23,5 s. Most food was fish, particularly klipfish Clinidae and pipefish Syngnathus, 60–160 mm long. The number of offspring produced can be related to food availability by interaction of difference in egg size, hatching asynchrony, and the preferential feeding by adults of the strongest-begging chick. There is a trend towards producing two chicks, normally those from the first two eggs to be laid.     

THE LAYING INTERVAL AND INCUBATION PERIOD OF ROCKHOPPER AND MACARONI PENGUINS

Williams, A. J. 1981. The laying interval and incubation period of Rockhopper and Macaroni Penguins. Ostrich 52: 226–229.

The laying interval and incubation period of Rockhopper Penguins Eudyptes chrysocome and Macaroni Penguins E. chrysolophus were studied at Marion Island in 1974–75 and 1976–77. On average, the laying interval was 4,4 and 4,5 days, the incubation period of second-laid eggs was 34,2 and 35,9 days and that of first-laid eggs was 39,1 and 38,0 days in Rock-hopper and Macaroni Penguins respectively. The laying interval in this genus is longer than that in other penguins. The incubation period is similar to that of most other penguins but the second-laid egg normally hatches before the first-laid egg. The long laying interval and the hatching sequence of the eggs both have important affects upon the mortality of eggs in the genus Eudyptes.     

MORPHOMETRICS AND BREEDING BIOLOGY OF THE WHITECHINNED PETREL PROCELLARIA AEQUINOCTIALIS AT SUB-ANTARCTIC MARION ISLAND

Berruti, A., Cooper, J. & Newton, I.P. 1995. Morphometrics and breeding biology of the Whitechinned Petrel Procellaria aequinoctialis at sub-Antarctic Marion Island. Ostrich 66: 74–80.

Aspects of adult morphometrics and the breeding biology of the summer-breeding Whitechinned Petrel at sub-Antarctic Marion Island, southern Indian Ocean, are given, based on a study conducted in 1980/91, along with additional observations on breeding success made in 1990191. It is concluded that Whitechinned Petrels at Marion Island are similarly sized and breed in a similar manner to other studied populations of the nominate race. The eradication of cats at Marion Island in 1991 should now lead to a slow population recovery.     

Breeding ecology of Red‐faced Cormorants in the Pribilof Islands,Alaska

ABSTRACT Red‐faced Cormorants (Phalacrocorax urile) are North Pacific endemics recognized as a vulnerable species, but little is known about their breeding ecology. We studied Red‐faced Cormorants on St. Paul Island, Alaska, from 1975 to 2009, with more detailed data collected in 2004 and 2005. Mean clutch sizes in 2004 (3.2 ± 0.8 [SD] eggs) and 2005 (3.1 ± 0.8 eggs) were similar to the long‐term average (2.9 ± 0.3 eggs from 1976 to 2009). The mean laying interval in 2004 and 2005 was 2.15 ± 0.80 d (N= 407), and the mean egg period (number of days between laying of an egg and hatching) was 31.1 ± 1.4 d (N= 158). Approximately 64 ± 17% of eggs hatched during the period from 1975 to 2009. The mean number of chicks per nest in 2004 and 2005 was 2.8 ± 0.8 (N= 232), and the mean number of fledglings per initiated nest in all years was 1.22 ± 0.52. Chicks fledged 46 to 66 d posthatching. In 2004 and 2005, the primary causes of egg loss were predation by Arctic foxes (Vulpes lagopus) and destruction of eggs and abandonment of nests due to storms. Starvation was the primary cause of nestling mortality in both years. Because chicks are dependent on parents to provide food for over 45 d, consistent near‐shore foraging opportunities must be available. From 1975 to 2009, Red‐faced Cormorants experienced only 1 yr of complete reproductive failure (1984). The consistent reproductive success of Red‐faced Cormorants suggests that conditions may be relatively stable for this species on St. Paul Island, or that the variability in their breeding ecology (e.g., phenology, clutch sizes, and incubation strategies) provides the flexibility needed to successfully fledge some chicks nearly every year.     

PREY SELECTION AND TEMPORAL VARIATION IN THE DIET OF SUBANTARCTIC SKUAS AT INACCESSIBLE ISLAND,TRISTAN DA CUNHA

Ryan, P.G., & Moloney, C.L. 1991. Prey selection and temporal variation in the diet of Subantarctic Skuas at Inaccessible Island, Tristan da Cunha. Ostrich 62:52-58.

More than 2 500 prey items of Subantarctic Skuas Cuthuructa anturcricu were identified from regurgitated pellets collected at a roost of non-breeding skuas during summer 1989–90 at West Point, Inaccessible'Is-land. Most prey items (96,5%) were birds, primarily burrow-nesting procellariiforms. Sixteen bird species were recorfed in the diet, but five secies accounted for 94,6% of identifiable prey remains: Whitebellied Storm Petrel Fieettu grullariu (53,5%), Whitefaced Storm Petrel Pelugodrorna marina 15,1%), Broad-billed Prion Pacaptilu vittutu (14,0%), Great Shearwater Puffinus gruvis (7,3%), and Iommon Diving Petrel Pelecunoids urinutrix (4,7%). Petrel chicks were important in the diet, particularly Great Shearwaters. The main non-avian prey were fish and goose barnacles Lepas sp., but their importance may have been underestimated. The remains of a rat Rattus sp. presumably were derived from the neighbouring island of Tristan da Cunha; rats are not known to occur on Inaccessible Island. Prey size affected seabird availability to skuas, and dietary composition vaned throughout the summer in relation to seabird breeding cycles. Both these factors reduce the value of skua diet as an indicator of the relative abundances of burrow-nesting petrels. There was no correlation between skua diet and estimates of breeding bird abundance, but this may be a consequence of studying non-breeding skuas. Subantarctic Skua diet in 1989–90 was similar to that recorded in previous years, with consistent seasonal trends between years.     

Desiccation and egg viability of the ragwort flea beetle,Longitarsus flavicornis (Coleoptera: Chrysomelidae)

A study was conducted to investigate the effect of desiccation on the survival of eggs of Longitarsus flavicornis. Eclosion of L. flavicornis eggs in laboratory trials decreased with increasing desiccation time between 0 days (93% hatching) and 42 days (no egg hatching) at 50±2% relative humidity and 23±2°C. Probit analysis indicated that 25, 50 and 99% mortality of L. flavicornis eggs occurred after 5.7, 9.3 and 50.4 days desiccation, respectively. Egg development varied between a minimum of 8 days at 7 days desiccation to a maximum of 15 days at 28 days desiccation. Hatching span did not differ between treatments with all eggs hatching within 12 days of each other. A relative humidity of 88–100% was measured under ragwort rosettes in non-drought field conditions. This would be expected to facilitate successful egg eclosion. However, the occurrence of summer drought could be detrimental to egg survival.     

Chick loss in the Falkland Skua Catharacta skua antarctica

Data on reproductive success of 110 Falkland Skua Catharacta skua antarctica pairs were gathered during the austral summers of 1988–1989 and 1990–1991 on New Island, Falkland Islands. Adults laid two eggs 2–3 days apart and began incubation with the first egg. For the years combined, 1.39 chicks per nest hatched and 0.84 chicks per nest fledged (fledging was defined as surviving to 16 days of age). Brood reduction was common; 43% of the two-chick broods were reduced to one, and mortality was concentrated on the younger chick. Although asynchronous hatching and differential death are consistent with Lack's brood reduction hypothesis, application of O'Connor's quantitative criterion revealed that sibling competition may not be responsible for the observed chick mortality. Furthermore, because no aggressive interactions between chicks were observed or detected indirectly, siblicide may be absent in this population. Instead, predation modified by a variety of factors may have led to the greater mortality of the second-hatched chick.     

Annual variation in breeding biology of gentoo penguins, Pygoscelis papua, at Bird Island, South Georgia

The breeding biology of the gentoo penguin, Pygoscelis papua , was studied over a three-year period (1986–1988) at Bird Island, South Georgia, with particular reference to birds of known age or breeding experience. Laying date varied significantly between all three years, being three weeks later in 1987, when the breeding population decreased markedly. Factors involved in the timing of breeding are discussed. Within years egg-laying was highly synchronous: 95% of clutches were initiated in 14·5 days or less. The incubation period was 35 days and the laying interval, between the two eggs, 3·3–3·4 days. Chicks creched when 25–30 days old, and this varied between years, possibly related to food supply and chick growth. Chicks left the colony for the first time between 75 and 85 days of age. The breeding population at Bird Island decreased by 20% and increased by 84% in successive years during the study period. Breeding success (chicks fledged per egg laid) varied between 0·33 and 0·65 within colonies, but for the whole island was very consistent over the three years: 0·45, 0·51 and 0·47. Overall, colony differences were not correlated between years. Disturbance from Antarctic fur seals, Arctocephalus gazella , is suggested as the cause of consistently lower breeding success at one colony. Mean egg weight varied annually, and with age of the breeding bird, nest location and, in one year, with laying date. Young, first-time breeders laid smaller eggs and had lower breeding success compared to older, experienced birds, similar to other seabirds. However, they differed from other species in laying on average earlier than older birds. The relationship between age, egg weight, laying date and breeding success is discussed in relation to predation and seasonal food supply.     

Patterns of Embryo Mortality in a Demersally Spawning Coral Reef Fish and the Role of Predatory Fishes

The biological significance of embryo mortality in demersally spawning coral reef fishes is poorly understood. Here we describe patterns of variation in embryo mortality in Pomacentrus amboinensis (Pomacentridae) at Lizard Island (Great Barrier Reef). The aim was to determine whether numbers of embryos hatched substantially differed from egg production, and if so, identify whether predatory fishes were a source of embryo mortality. Spawning success (number of eggs laid), embryo mortality (proportion of embryos that died prior to hatching) and number of embryos hatching were estimated from daily maps of clutches laid on artificial surfaces (PVC tiles) defended by nesting males. Patterns of variation in eggs laid, embryo mortality and numbers of embryos hatched were examined at three spatial scales: (1) among widely-spaced locations around the island; (2) between adjacent reef slope and patch reef habitats occupied by P. amboinensis at a single location; and (3) among different males within these two habitats. The embryo mortality was extremely high, with a mean of 25.9pm ± 6.2% (S.E.) for 4 locations examined in 1994 and a mean of 69.2pm ± 2.9% for two habitats surveyed in 1995. There were no significant differences in embryo mortality among locations or habitats in either year. This meant that spatial patterns in the number of embryos hatching reflected differences in the number of eggs laid on tiles. Embryo mortality was extremely variable on the scale of individual territories, with embryo mortality commonly ranging from 0% to 100%. Much of the mortality could be attributed to diurnal predatory fishes, especially the wrasse Thalassoma lunare. However, variation in predator densities did not explain spatial patterns in embryo mortality rates. Both solitary and group predatory behaviour was observed, with groups often causing 100% embryo mortality. The level of embryo mortality observed suggests that predation prior to hatching may have a substantial effect on the reproductive output of populations of this demersal-nesting fish.     

Drivers of the breeding success of American Oystercatchers (Haematopus palliatus frazari) at a critical site in Sinaloa,Mexico

Understanding breeding phenology and success can elucidate population dynamics, which is especially important for species in need of conservation. We describe the factors affecting the breeding biology of American Oystercatchers (Haematopus palliatus frazari) at El Rancho Island, a critical site that contains ~ 7% of the total estimated population, on the coast of Sinaloa, Mexico. We monitored 192 nests over four years (2016–2019). The breeding season lasted from March to June and mean laying dates differed among years, with the mean laying date in 2019 an average of 20 days earlier than in 2016. Clutch sizes decreased as the breeding season progressed. Both breeding success and productivity differed among years, with the lowest values in 2016 (30% hatching success and 0.6 chicks/nest) and the highest in 2019 (66% hatching success and 1.2 chicks/nest). Hatching success was affected by year, laying date, type of habitat, and distance to the high tide line. American Oystercatchers that laid eggs earlier in the season, used mixed marsh and dune habitat, and with nests relatively close to the waterline (< 50 m) had greater breeding success. Overall, however, the breeding success of American Oystercatchers was low and influenced by a combination of several intrinsic and extrinsic factors. Management measures may be required to increase breeding success and ensure the conservation of this subspecies.     

Contrasting effects of GPS device and harness attachment on adult survival of Lesser Black‐backed Gulls Larus fuscus and Great Skuas Stercorarius skua

Telemetry has become an important method for studying the biology and ecology of animals. However, the impact of tracking devices and their method of attachment on different species across multiple temporal scales has seldom been assessed. We compared the behavioural and demographic responses of two species of seabird, Lesser Black‐backed Gull Larus fuscus and Great Skua Stercorarius skua, to a GPS device attached using a crossover wing harness. We used telemetry information and monitoring of breeding colonies to compare birds equipped with a device and harness, and control birds without an attachment. We assessed whether tagged birds have lower short‐term breeding productivity or lower longer term overwinter return rates (indicative of overwinter survival) than controls. For Great Skua, we also assessed whether territory attendance within the breeding season differed between tagged and control birds. As with previous studies on Lesser Black‐backed Gull, we found no short‐term impacts on breeding productivity or long‐term impacts on overwinter return rates. For Great Skua, there was no evidence for impacts of the device and harness on territory attendance or breeding productivity. However, as found by a previous study of Great Skuas using a different (body) harness design, there was strong evidence of reduced overwinter return rates. Consequently, a device attached using a wing harness was considered suitable for long‐term deployment on Lesser Black‐backed Gulls, but not on Great Skuas. These findings will inform the planning of future tracking studies.     

Patterns in the abundance,phenology, and hatching of the resting egg stage of the invasive zooplankter <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis>: implications for establishment

To examine how dormancy contributes to the establishment and persistence of Bythotrephes longimanus, we investigated resting egg production and hatching in relation to the demography of the planktonic stage and environmental conditions in Island Lake Reservoir (USA). During a 3-year study, the largest contribution to the egg bank occurred in autumn and most eggs hatched in spring, but we also detected some resting egg production and hatching in summer. The difference between summer and late autumn densities of eggs in sediments averaged 47% (range 0–98%) for 18 sites throughout the reservoir, which was similar to experimental estimates of in situ hatching fraction of 67% for eggs in the spring and summer following their production. Based on emergence traps, neonates hatch in the field during May and June. We estimated mortality rates of 64% for resting eggs and embryos, and 59% for newly emerged neonates. Although hatching fraction saturated at the same level, eggs incubated offshore hatched later than those nearshore where water temperature was warmer and light was detectable at the sediment surface. Low dissolved oxygen concentration did not significantly reduce hatching fraction but resulted in some eggs that initiated development but failed to hatch. Collectively, our results demonstrate substantial annual turnover in the resting egg bank of B. longimanus and high mortality of resting eggs during recruitment from the egg to the first molt of the planktonic stage. These patterns suggest that propagule pressure in the form of resting eggs requires large numbers for establishment, and that considerable post-establishment resting egg production is necessary for inter-annual persistence.     

The breeding biology of the Dalmatian Pelican Pelecanus crispus

The breeding biology of the Dalmatian Pelican Pelecanus crispus , a vulnerable bird species in the Palaearctic, has been studied for 7 years at Lake Mikri Prespa, a continental wetland and Tsoukalio lagoon, a coastal wetland within the Amvrakikos Gulf. The two colonies showed stability, with fluctuations in the number of breeding attempts each year varying by about 30% over a period of 7 years. The date of arrival at the breeding sites and the date of laying of the first egg varied between mid-February and mid-March. The egglaying period (including renesting) varied between 18 and 114 days between years. The annual average clutch size varied between 1.60 and 1.94 eggs per nest. The incubation period averaged 31.4 ± 1.4 days. The overall hatching success varied from 36% to 70%. Egg losses were mainly due to nest abandonment, infertile eggs and eggs rolled from the nests. The Dalmatian Pelican chicks took 11–12 weeks to fledge. Nestling mortality was very low in contrast to other species of pelican. Such a low nestling mortality explains why the breeding success each year is largely explained by the hatching success.     

HARTLAUB'S GULL: EGGS AND INCUBATION

A.J. Williams. 1990. Hartlaub's Gull: eggs and incubation. Ostrich 61:93-96.

At Marcus Island, South Africa in 1979 Hartlaub's Gulls Larus hartlaubii laid eggs between 31 January and 28 February. Clutches were of one to three eggs; and 49% consisted of two eggs. Egg composition, and intra-clutch variation in egg size and weight, are reported. The laying interval was two days, the incubation period 25 days, and the hatching interval 0,8 days.     

The diet of the Wandering Albatross Diomedea exulans at Subantarctic Marion Island

Summary The diet of the Wandering Albatross at Subantarctic Marion Island was studied by inducing recently fed chicks to regurgitate and by stomach flushing adults about to feed chicks. Liquid comprised 70.2% of stomach content mass recovered from chicks. Solid material comprised cephalopods (58.6% by mass), fish (36.5%) and crustacean, cetacean and seabird material as minor items. Twenty-three taxa of cephalopods were identified, the onychcteuthid squid Kondakovia longimana being the most important. Estimated average mass of squid was 694 g with a maximum of over 8 kg. Diet of the Wandering Albatross at Marion Island was broadly similar to that at other studied localities. The high proportion of cephalopods known to float after death in the diet, and the deep-water habits of the few fish identified, suggest that scavenging plays an important role in foraging behaviour.     

Proceedings of the New Zealand Society for Parasitology Inc.

Abstract

A study of the nesting habits and breeding biology of blue penguin Eudyptula minor was undertaken over the 1995–96 and 1996–97 breeding seasons on Matiu‐Somes Island, Wellington, New Zealand. Male and female blue penguins tended to be faithful to both mates and nest sites, although there was insufficient evidence to detect any association between a bird's breeding success in 1995 and a subsequent change of mate or nest in 1996. Over the 1995 and 1996 seasons the recorded hatching success (0.51 ±0.11 and 0.63 ± 0.10 respectively), fledging success (0.81 ±0.12 and 0.85 ±0.10 respectively) and reproductive success (0.41 + 0.11 and 0.54 ± 0.11 respectively) were similar each season. There was no significant difference between the proportion of eggs laid, or eggs hatched and chicks fledged, between the two seasons. The mean number of chicks raised over the two seasons was 0.94 ± 0.05 per nest. Replacement clutches were laid by 11 per cent of failed breeders in each season, but only in 1996 were they successful in fledging chicks.

No significant difference was found between the breeding success of the Matiu‐Somes Island blue penguin colony recorded during this study and a previous study undertaken on the island 40 years ago.     

Breeding success and the question of clutch size of Northwestern Crows Corvus caurinus

The breeding biology of two island populations of the Northwestern Crow was studied in British Columbia over a period of five years. Both populations laid an average of four eggs per clutch, of which approximately 75% hatched. More young survived to fledge on Mandate than on Mitlenatch Island. The young from nests close (< 100 m) to the beach on Mitlenatch had a higher survival rate than those from further inland. The number of eggs lost or failing to hatch was lowest in clutches of four eggs. There was a non-significant trend for chick survival to be inversely related to clutch size. The net result was that clutches of five eggs produced no more young than did clutches of four eggs. It is suggested that the major limiting factor on clutch size is food availability but the decreased hatching success of any remaining eggs once hatching has started is also a contributing factor.