Seabird associations in Pacific equatorial waters

Seabirds were counted along the same cruise tracks in the eastern tropical Pacific (10°øN-10°øS and 140°ø-90°øW) each spring and autumn for 8 years, 1984–1991. During spring, three species groups were apparent among eight species seen in five or more years: (1) Leach's Storm-petrel Oceanodroma leucorhoa and Wedge-rumped Storm-petrel Oceanodroma tethys , which feed on neuston by surface seizing; (2) Black-winged Petrel Pterodroma nigripennis and White-winged Petrel Pterodroma leucoptera , which feed on neuston and micronekton by surface seizing; (3) Juan Fernandez Petrel Pterodroma externa , Wedge-tailed Shearwater Puffinus pacificus and Sooty Tern Sterna fuscata , which feed on micronekton driven to the surface by foraging tuna. During autumn, only one group was identified from the seven species seen in five or more years: Leach's Storm-petrel associated with either Wedge-rumped Storm-petrel or Juan Fernandez Petrel and/or White-winged Petrel. Annual variability in assemblage composition was more extreme in the autumn and thus was similar to variation in physical and biological factors linked to the El Niño-Southern Oscillation cycle.     

Key elements in achieving a successful recovery programme: A discussion illustrated by the Gould's Petrel case study

Summary   Surprisingly few faunal taxa worldwide have experienced an improvement in conservation status through direct conservation action. One of the few is Gould's Petrel ( Pterodroma leucoptera leucoptera ) – a threatened species that breeds only in New South Wales. In the early 1990s, the breeding population of this subspecies was small (<250 pairs) and declining. Each year, adult mortality at the breeding grounds exceeded the number of young produced. A recovery programme, focused on reducing adult mortality, commenced in 1993. As a result of the recovery actions undertaken, the Gould's Petrel is now increasing in numbers. Also, the rainforest where this seabird breeds is now regenerating after being degraded for almost a century by the introduced European Rabbit ( Oryctolagus cuniculus ). The creation of artificial nesting habitat and the development of effective translocation procedures have led to the establishment of a second breeding colony of Gould's Petrel, further reducing the risk of extinction.
In this paper, we explore the key elements we believe to be responsible for the success of this particular recovery programme: (i) a strong underpinning of robust ecological research; (ii) adaptive management; (iii) monitoring and reporting; (iv) a multidisciplinary approach; and (v) a willingness to accept risk. We conclude with some suggestions to improve the current recovery planning process.     

Endozoochory by ducks: influence of developmental stage of Bythotrephes diapause eggs on dispersal probability

Abstract. This paper evaluates whether the recent expansion of Bythotrephes longimanus Leydig (Crustacea: Onychopoda) may be a result of endozoochorous avian dispersal. In three experiments, we investigated the survival of diapause eggs in newly produced and end-of-winter developmental stages after their passage through the digestive tract of four species of ducks. Resistance of eggs to digestion was low for both developmental stages (< 12%). Most eggs (67–95%) were recovered by four hours after ingestion, with a longer maximum retention time for newly produced (22 h) than end-of-winter eggs (4–6 h). Ingestion had a detrimental effect on viability: only eggs retrieved one hour after ingestion hatched and the proportion of those ingested that produced viable neonates was low (0.5% for newly produced and 0.3–3% for end-of-winter eggs). We conclude that the probability of endozoochorous dispersal by individual ducks is low but becomes significant when considering the thousands of ducks moving among wetlands. Endozoochorous dispersal of B. longimanus would most likely involve the transport of newly produced diapause eggs from north to south, during the autumn migration of ducks. Based on flight speed estimates of ducks we estimate dispersal probability to drop sharply at distances over 60–80 km.     

Breeding biology and success of the Bearded Vulture Gypaetus barbatus in the eastern Pyrenees

We present data from an extensive study of Bearded Vulture Gypaetus barbatus breeding biology in the Pyrenees from 1992 to 1999. Average laying date was 6 January (range 11 December to 12 February, n  = 69) with no significant differences between years. Eighty per cent of clutches were of two eggs ( n  = 20) and average incubation was 54 days (range 52–56, n  = 14). Hatching occurred on average between 21 February and 3 March (range 5 February–7 April) and the first and last chicks fledged in 21–27 May and 20 July, respectively. The average chick age at fledging was 123 days (range 103–133, n  = 20). Bearded Vulture density increased significantly during the study period. Breeding success and productivity declined apparently as a consequence of the increase in the percentage of breeding failures during incubation and chick rearing, most during the hatching period. The factors that may determine breeding failure and the decline in breeding performance are analysed and management recommendations for more effective conservation measures are discussed.     

Differential habitat use by Acadian Nelson's sharp-tailed sparrows: implications for regional conservation

ABSTRACT.   Nelson's Sharp-tailed Sparrows ( Ammodramus nelsoni ) that breed along the Atlantic coast of North America (Acadian subspecies subvirgatus ) are considered saltmarsh specialists. However, these sparrows occasionally use upland habitats, such as hayfields. To evaluate the importance of hayfields as breeding habitat, we studied populations of A. n. subvirgatus in saltmarsh and hayfields in Nova Scotia, Canada, in 2004 and 2005. We monitored relative abundance and breeding phenology at 64 point-count stations (48 in hayfields and 16 in saltmarsh) and used an ordinal (0–5) observational index to quantify reproductive activity. A. n. subvirgatus showed more evidence of reproductive activity in saltmarsh (44% of point-count stations) than hayfields (28%; P = 0.07). However, there was no difference in either mean reproductive activity (saltmarsh = 0.83, hayfields = 0.53; P = 0.69) or mean relative abundance (saltmarsh = 0.27, hayfields = 0.26; P = 0.93). Although A. n. subvirgatus apparently breeds primarily in saltmarsh, hayfields appear to be an alternative breeding habitat. Use of hayfield habitat by A. n. subvirgtus , however, seems to vary between southern Maine and eastern Canada, suggesting that management plans will require approaches uniquely tailored to specific regions.     

Cats and seabirds: effects of feral Domestic Cat Felis silvestris catus eradication on the population of Sooty Terns Onychoprion fuscata on Ascension Island, South Atlantic

The population of Sooty Terns Onychoprion fuscata breeding on Ascension Island in the Atlantic Ocean was monitored over 17 years (1990–2007). This period spanned the programme of feral Domestic Cat Felis silvestris catus eradication from the island, which commenced in 2001 with the last Cat recorded in 2004. We report on the abundance of Sooty Terns and Black Rats Rattus rattus before and after Cat eradication. The Sooty Tern breeding population in the 1990s averaged 368 000 and Cats were killing Terns at an average rate of 33 adults per night. Following Cat eradication, adult Terns are no longer predated. However, egg predation by both Rats and Common Mynas Acridotheres tristis has continued with Mynas destroying more eggs than Rats. Unexpectedly, we observed a change in Rat predatory behaviour. Following Cat eradication, Rats have become a major predator of Sooty Tern chicks. Despite this change, the Tern population has shown a season-on-season increase since Cat eradication, 48.8% in 2005, 8.2% in 2006 and 6.1% in 2007, and the breeding population increased to 420 000 birds in 2007. Incubation success improved from 66.0 to 84.4% during Cat eradication, before dropping down again to 67.9% after Cats were eradicated and Rat control measures were introduced. Index traplines were set for Rats and Rat numbers fluctuated widely immediately after Cats were eradicated but there were no significant differences that could be attributed to changes in Cat numbers. Ascension Island Sooty Terns breed every 9.6 months and juveniles defer breeding for seven seasons. Hence 2008 is the first year in which an increase in the breeding Sooty Tern population directly attributable to Cat eradication is likely to be detected. We conclude that long-term monitoring is essential to guide conservation practice even in this relatively simple predator–prey system.     

Reproduction of spined loach, Cobitis taenia, (Cypriniformes; Cobitidae) under laboratory conditions

A simple and reliable method is described for breeding spined loach, Cobitis taenia Linnaeus, 1758, under laboratory conditions. Three 40 L aquaria were each provided with a thick tuft of moss placed on top of a gauze-covered plastic box to serve as a spawning site. Ovoposition always occurred in the most densely available vegetation. The nonadhesive eggs fell through the gauze into the box. The spined loach is a fractional spawner releasing eggs in 14–18 batches at intervals of 2–23 (median 6) days. The total number of eggs per female was 2905–4282 during the reproductive season of 101–120 days. Yolks measured 1.14 ± 0.07 mm and eggs were 2.54 ± 0.22 mm in diameter. Total larval length was 5.03 ± 0.34 mm at hatching and 6.77 ± 0.34 mm at the beginning of exogenous feeding. The method allowed the rearing of numerous young for conservation measures and experimental investigations.     

Seasonal abundance of nonbreeding Piping Plovers on a Georgia barrier island

ABSTRACT.   Although breeding populations of Piping Plovers are well studied, their winter distribution is less clear. We studied the seasonal abundance of nonbreeding Piping Plovers ( Charadrius melodus ) during the winters of 2003–2004 and 2004–2005 on Little St. Simons Island (LSSI), Georgia. Our objectives were to determine the relative abundance of individuals from three breeding populations at LSSI, and identify possible differences among populations in arrival time, winter movements, or departure time. We observed up to 100 Piping Plovers during peak migration, and approximately 40 plovers wintered at LSSI. From July 2004 to May 2005, approximately 20% of the Great Lakes breeding population used LSSI. Plovers were not present at LSSI during June. All breeding populations of Piping Plovers had similar patterns of temporal occurrence on LSSI, suggesting no need for population-specific management plans at this site. Our results suggest that LSSI is among the most important wintering sites on the Atlantic coast for Piping Plovers, especially for individuals from the endangered Great Lakes population.     

Nesting, overwintering, and conservation of the Crab Plover Dromas ardeola in central Eritrea

We describe 30 new nesting sites of the Crab Plover Dromas ardeola , the main breeding grounds of which were largely unknown, and for which fewer than 30 colonies had been confirmed since 1970. Our survey included 90 islands, 53% of those existing, in the Dahlak and Howakil archipelagoes, and off the coast of central Eritrea. Colony size varied between 20 and 400 nests. We estimate the numbers of Crab Plovers breeding in central Eritrea at 5000–6000 pairs, i.e. about 50% of the known world breeding population. We describe two cases of probable replacement clutches, a feature unrecorded in this species. Black Rats Rattus rattus seem unable to open Crab Plover eggs, and do not seem to be a threat. Crab Plover colonies are traditionally exploited by local fishermen for collection of eggs, an activity that has increased recently. Our new records solve only partially the problem of the 'missing' colonies that are required to account for the world wintering population of 60 000–80 000 birds, and thus other breeding sites remain to be discovered, probably in southern Eritrea, Sudan and Somalia. We estimated that there are 4800–6500 Crab Plovers overwintering within central Eritrea, making it an important wintering ground for the species.     

Variation in circulating corticosterone levels is associated with altitudinal range expansion in a passerine bird

Organisms frequently need to adjust physiological mechanisms to successfully breed in novel habitats. To explore how some populations physiologically acclimate to novel environmental conditions while others do not, we examine three subspecies of the white-crowned sparrow, Zonotrichia leucophrys. Of these subspecies, Z. l. pugetensis has expanded its breeding range to high altitude over the last 60 years. We investigate physiological acclimation to high altitude conditions by comparing circulating levels of glucocorticoids among Z. l. gambelii, which only breeds at high altitude, Z. l. nuttalli, which only breeds at low altitude, a population of Z. l. pugetensis that breeds at low altitude, and a Z. l. pugetensis population that now breeds at high altitude. Glucocorticoids mediate physiological and behavioral responses to environmental conditions and are constitutively secreted, but can also be released facultatively. We hypothesized that elevation of the glucocorticoid corticosterone (CORT) may facilitate breeding in high altitude environments. We tested this hypothesis by comparing baseline and stress-induced CORT levels of subspecies breeding at low altitude, Z. l. pugetensis and Z. l. nuttalli, to subspecies breeding at high altitude, Z. l. pugetensis and Z. l. gambelii. We found that populations breeding at high altitude exhibit higher baseline and stress-induced levels of CORT. Additionally, we found that Z. l. pugetensis exhibit greater variation in the stress-induced CORT response. These results suggest an importance of modulation of hormonal mechanisms in facilitating breeding in high altitude environments, and that variation in these mechanisms may be associated with facilitating altitudinal range expansion.     

Reproduction and survival of Glaucous Gulls breeding in an Arctic seabird colony

ABSTRACT.   Despite being widespread and easily observed, little is known about the life history of Glaucous Gulls ( Larus hyperboreus ). From 1984 to 2007, we examined their breeding biology and demography at Coats Island, Nunavut, Canada, where they nest alongside a colony of 30,000 pairs of Thick-billed Murres ( Uria lomvia ). The gulls fed mainly on murre eggs and chicks and by scavenging adult carcasses. The median age at first breeding was 5 yr, and the mean age was 4.8 ± 0.9 yr. Adult survival was estimated as 0.84 ± 0.03 (SE). The mean clutch size was 2.56 eggs and the mean number of young reared per year was 1.6 (range = 0.9–2.2). Birds reared at the colony provided 40% of recruits. Assuming that survival of locally reared chicks that emigrated was similar to that of chicks that returned to the colony, about 22% of the young gulls survived to breeding age. The timing of breeding by Glaucous Gulls appeared related to the timing of laying by murres. Although the demographic characteristics of Glaucous Gulls in our study were similar to those of populations of other large gulls, adult survival was at the lower end of the range for populations of large Larus gulls. There is some evidence that Glaucous Gulls exhibit lower survival than large gulls breeding in temperate areas, possibly because of contaminant burdens. In general, however, the demographic characteristics of large gulls show little variation and are probably a product of their common phylogeny.     

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.     

Population structure of loggerhead shrikes in the California Channel Islands

The loggerhead shrike (Lanius ludovicianus), a songbird that hunts like a small raptor, maintains breeding populations on seven of the eight California Channel Islands. One of the two subspecies, L. l. anthonyi, was described as having breeding populations on six of the islands while a second subspecies, L. l. mearnsi, was described as being endemic to San Clemente Island. Previous genetic studies have demonstrated that the San Clemente Island loggerhead shrike is well differentiated genetically from both L. l. anthonyi and mainland populations, despite the fact that birds from outside the population are regular visitors to the island. Those studies, however, did not include a comparison between San Clemente Island shrikes and the breeding population on Santa Catalina Island, the closest island to San Clemente. Here we use mitochondrial control region sequences and nuclear microsatellites to investigate the population structure of loggerhead shrikes in the Channel Islands. We confirm the genetic distinctiveness of the San Clemente Island loggerhead shrike and, using Bayesian clustering analysis, demonstrate the presence and infer the source of the nonbreeding visitors. Our results indicate that Channel Island loggerhead shrikes comprise three distinct genetic clusters that inhabit: (i) San Clemente Island, (ii) Santa Catalina Island and (iii) the Northern Channel Islands and nearby mainland; they do not support a recent suggestion that all Channel Island loggerhead shrikes should be managed as a single entity.     

Susceptibility of immature stages of Chrysoperla rufilabris (Neurop., Chrysopidae) to pyriproxyfen, a juvenile hormone analog

Effects of pyriproxyfen (Knack), a juvenile analog, at three concentrations (10, 50 and100 mg [AI]/l), on survival and development of all immature stages of Chrysoperla rufilabris (Burmeister), were determined in the laboratory. Pyriproxyfen significantly reduced the survival rates when eggs, first and third instars were treated, but not when the second instars and pupae were treated. When eggs were treated, the two higher concentrations reduced the eggs viability by 33.3–50%, and only 0.0–6.7% developed to adults. The lowest concentration of pyriproxyfen (10 mg [AI]/l) caused high mortality on third instars, not on other stages, indicating the third instar was the most vulnerable stage. Pyriproxyfen had significant effects on development for all immature C. rufilabris that successfully developed to adults with variations among the developmental stages and concentrations. The overall developmental duration from eggs to adults when eggs, first, and third instars were treated were 2.6–4.2, 2.4–4.1 respectively, and 6.0–7.1 d longer than those in water control, respectively. However, the overall developmental durations from eggs to adults were 0.5–1.2 d shorter than in water control when the second instars were treated with pyriproxyfen. The compatibility of pyriproxyfen with natural enemies in integrated pest management programs is discussed.     

OBSERVATIONS ON THE LAVA GULL LARUS FVLIGINOSUS

Lava Gulls Larus fuliginosus live as scavengers and unspecialized predators along the shores of the Galapagos Islands. Although they concentrate locally at places where refuse is available, their breeding density is low: eight breeding pairs were found along a stretch of 35 miles of the coast of Indefatigable Island. The total (world) population is likely to be less than 300–400 breeding pairs.
Their low breeding density and small total population is attributed to the fact that they are confined to linear feeding grounds of limited extent, which provide a sparse food supply for much of the year.
Lava Gulls nest solitarily, usually in sheltered places near coastal lagoons; all the nests found were at least two miles from any other known site. The clutch consists of two eggs, incubation (one case) lasts 32–33 days, and the fledging period is about 60 days.
Breeding takes place throughout the year, with no apparent peak. Individual cycles of 9–12 months have been recorded.
Observations are given on behaviour and displays, and on the sequence of plumage change and moult in the first two years of life.     

Adult Brünnich's Guillemots Uria lomvia balance body condition and investment in chick growth

To investigate the covariation of adult body condition and nestling growth, we weighed adult Brünnich's Guillemots Uria lomvia rearing chicks at Coats Island, Nunavut, Canada, each year between 1988 and 2002. We estimated chick mass at 14 days for a sample of chicks reared in the same years. Adult mass and chick mass at 14 days were highly correlated, suggesting that, as feeding conditions deteriorate, adults compromise by reducing their own body reserves, while at the same time delivering less food to their offspring. We compared the prediction of the least-squares regression for the Coats Island data with observations made at Digges Island, a much larger colony about 300 km away, where birds are similar in linear body measurements to those at Coats Island and have a similar body mass while incubating. Adult mass at Digges Island averaged 11% less during chick-rearing than during incubation, compared with only a 5% difference at Coats Island. Mean chick mass at 14 days at Digges Island was lower in all years than was observed for chicks at Coats Island in any year. The observed 14-day chick masses at Digges Island in two years were close to values predicted by adult mass and somewhat lower in two other years (those when chick growth was slowest). At Digges Island, the distribution of mass for brooding adults was right skewed and suggested a lower threshold at 800–850 g, below which Brünnich's Guillemots terminate breeding. We conclude that the correlation between adult and chick mass represents a dynamic equilibrium in which adults simultaneously adjust their own energy reserves and their delivery rate to the chick. This compromise must be based on behavioural choices made by individual birds and is unlikely to be a passive consequence of fluctuating conditions.     

Life history and production of Paranephrops zealandicus in a forest stream, with comments about the sustainable harvest of a freshwater crayfish

1. Life history and production were assessed for the crayfish Paranephrops zealandicus in three reaches of a headwater stream with a catchment of regenerating coniferous-broadleaf forest in the south-east of the South Island of New Zealand.
2. Crayfish density ranged from 3 to 4 m⁻² in riffles and 4–12 m⁻² in pools, depending on reach. Crayfish biomass (4–33 g AFDW m⁻²) and annual production (2–11 g AFDW m⁻²) were high compared with values reported elsewhere, while P:B ratio was low (0.33–0.43). This substantial production was dependent primarily upon high biomass rather than high growth rate.
3. The crayfish of this population rank amongst the longest lived and slowest growing ever recorded. Individuals estimated to be 16+ year of age were not uncommon. Females became reproductively active at 6+ year. Fewer than 4% of females carried eggs, and young remained attached to females for at least 15 months.
4. We propose that characteristics of this population are the consequence of a cool thermal regime (mean daily stream temperature = 7.0 °C, range 1.8–11.9 °C), and that low biomass turnover and poor reproductive rate precludes any sustainable commercial harvest of crayfish from streams in New Zealand with similar thermal regimes.     

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.     

Breeding biology and conservation of the Black-vented Shearwater Puffinus opisthomelas

The Black-vented Shearwater Puffinus opisthomelas is endemic to the Pacific coast of Baja California, Mexico. We studied the breeding biology of this species at Natividad Island in 1997 and 1998. The colony at Natividad Island covers approximately 2.5 km² and we estimated there to be 114 455 (± 27 520 95% CI) burrows in the colony. In 1997 burrow occupancy was 66.9%, providing a population estimate of 76 570 (± 18 411 95% CI) breeding pairs, representing about 95% of the world's population of this species. In 1997 the peak in egg laying occurred in early March and hatching began on 7 May. The incubation period averaged 51 days (± 6 sd) and chick rearing averaged 69 days (± 3 sd). In 1998 burrow occupancy was lower (19.6%) and nest initiation was later (peak egg laying in mid-April), perhaps a result of El Niño conditions that prevailed in the Eastern Pacific at that time. We calculated that the development of the town and roads on Natividad Island have destroyed over 15% (26 532 burrows) of the breeding habitat on the island.