Leach's Storm-petrel Oceanodroma Leucorhoa Research Articles

Population genetic structure and long‐distance dispersal among seabird populations: Implications for colony persistence

Dramatic local population decline brought about by anthropogenic-driven change is an increasingly common threat to biodiversity. Seabird life history traits make them particularly vulnerable to such change; therefore, understanding population connectivity and dispersal dynamics is vital for successful management. Our study used a 357-base pair mitochondrial control region locus sequenced for 103 individuals and 18 nuclear microsatellite loci genotyped for 245 individuals to investigate population structure in the Atlantic and Pacific populations of the pelagic seabird, Leach's storm-petrel Oceanodroma leucorhoa leucorhoa. This species is under intense predation pressure at one regionally important colony on St Kilda, Scotland, where a disparity between population decline and predation rates hints at immigration from other large colonies. AMOVA, F(ST), Φ(ST) and Bayesian cluster analyses revealed no genetic structure among Atlantic colonies (Global Φ(ST) = -0.02 P > 0.05, Global F(ST) = 0.003, P > 0.05, STRUCTURE K = 1), consistent with either contemporary gene flow or strong historical association within the ocean basin. The Pacific and Atlantic populations are genetically distinct (Global Φ(ST) = 0.32 P < 0.0001, Global F(ST) = 0.04, P < 0.0001, STRUCTURE K = 2), but evidence for interocean exchange was found with individual exclusion/assignment and population coalescent analyses. These findings highlight the importance of conserving multiple colonies at a number of different sites and suggest that management of this seabird may be best viewed at an oceanic scale. Moreover, our study provides an illustration of how long-distance movement may ameliorate the potentially deleterious impacts of localized environmental change, although direct measures of dispersal are still required to better understand this process.

Relationship between Body Water and Lipid in Three Seabird Species: Leach's Storm-Petrel, Rhinoceros Auklet and Black-Tailed Gull

Abstract Measuring the individual body conditions of living birds is essential for understanding tradeoffs in life-history studies, especially in long-lived species. The aim of this study was to further develop a method for measuring body condition (lipid content), without killing birds. In theory, the lipid content mass in the body should have a close inverse relationship with water mass. Using this relationship, body condition can be evaluated without killing because the amount of water in the body can be estimated in live birds. However, the inverse relationship has only been shown to exist in a few studies of bird species. In this study, significant inverse relationships between water and lipid contents of three seabird species, Leach's Storm-Petrel Oceanodroma leucorhoa, Rhinoceros Auklet Cerorhinca monocerata and Black-tailed Gull Lams crassirostris, were shown. These facts highlight that body condition (lipid content) , can be estimated from the water content of the body.

Maximum Load-Carrying During Takeoff of Leach's Storm-PetrelOceanodroma leucorhoaand Cassin's AukletPtychoramphus aleuticus

Abstract. Birds at-sea increase body mass as a consequence of food consumption and plumage wettability. However, little is known about the effect of maximum extra load on takeoff of aquatic birds. Experimental evaluation of maximum load-lift during takeoff was performed on a wing-propelled diver with high wing loading, Cassin's Auklet Ptychoramphus aleuticus, and on a surface feeder with low wing loading, Leach's Storm-Petrel Oceanodroma leucorhoa. Leach's Storm-Petrel supported a maximum extra load of 45% of its body mass, and that of Cassin's Auklet was 25%. The relation of maximal load to food transport and plumage wettability indicates that the storm-petrel and the alcid maintain safety load margins of 31% and 8% of the maximum supported extra load during takeoff, respectively. Load margin showed by storm-petrels suggests an enhanced flight performance, increasing specific lift during foraging; meanwhile that of auklets allows for reduction of specific buoyancy during diving.

Seabird numbers and prey consumption in the North Atlantic

Abstract We compared seasonal composition, abundance, and biomass of seabirds between the Northeast (ICES region) and Northwest (NAFO region) Atlantic fisheries regions to identify differences in community assemblage and prey consumption. Seabirds were more abundant in the Northwest Atlantic, but biomass was greater in the Northeast. This disparity resulted from enormous numbers of little auks Alle alle breeding in West Greenland and of Leach's storm-petrels Oceanodroma leucorhoa breeding in Newfoundland, plus large numbers of non-breeding shearwaters Puffinus spp. entering southern NAFO areas in summer. The Northeast Atlantic communities were dominated numerically by northern fulmars Fulmarus glacialis, large auks Uria spp., and the Atlantic puffin Fratercula arctica. Seabirds occupying the North Atlantic consume approximately 11 × 106 t of food annually. Overall consumption rates peak during summer as a result of increased breeding activity and seasonal movements of birds into the North Atlantic. Because of the greater biomass of birds in the northeast, consumption (mainly by piscivores) in ICES areas was approximately 20% higher than that in NAFO areas, where planktivores dominate. NAFO areas had, however, a much greater consumption rate per unit area than ICES areas. Comparative studies such as these could prove informative in assessing large predator responses to the influence of fishing and ocean-scale climate change.

Effects of investigator disturbance on hatching success and nest-site fidelity in a long-lived seabird, Leach's storm-petrel

Long-lived animals are expected to reduce reproductive effort when breeding conditions are unfavorable, therefore seabirds may be especially sensitive to investigator disturbance. In a non-threatened procellariiform, Leach's storm-petrel Oceanodroma leucorhoa, we examined whether the frequency and the time of day of investigator disturbance influenced hatching success, and if disturbance affected hatching success and nest-site fidelity in the subsequent breeding season. Birds used in this study had received little or no investigator disturbance during the prior decade. Hatching success was significantly influenced by the frequency, but not the time of day, of disturbance. Weekly and daily handling of parents reduced hatching success by 50 and 56% compared to the control group. Most failures (91%) were caused by egg desertion, and all the deserted eggs belonged to pairs in the weekly and daily groups. During the subsequent breeding season, the hatching success of disturbed pairs that continued to breed together returned to normal levels. However, 37% more disturbed pairs than control pairs deserted the nesting burrows they had used in the previous year. Since most changes in nest site also result in mate change, investigator disturbance may have had long-term negative effects on reproductive success as well. Our results demonstrate that both weekly and daily investigator disturbance during incubation greatly reduced the hatching success and subsequent nest-site fidelity of naı̈ve Leach's storm-petrels.

Indirect effects of the availability of capelin and fishery discards:gull predation on breeding storm-petrels

The Northwest Atlantic has undergone large-scale perturbations which have had profound effects on pelagic food webs. Over the past century, the increasing availability of human refuse and fishery discards have promoted the growth of Larus gull populations. During the 1990s, cold surface-water events have delayed the inshore movements of spawning capelin Mallotus villosus and fisheries closures have eliminated massive tonnages of discards. These circumstances have interacted to intensify food stress on gulls. We investigated gull predation in a large colony of Leach's storm-petrels Oceanodroma leucorhoa as an indirect consequence of the availability of prey and fishery discards. Predation did not differ between storm-petrels nesting in forest and open habitats even though gull nests were more often in close proximity to storm-petrel burrows in open habitat. In 1996 and 1997, gull predation on storm-petrels varied seasonally, with a significant decrease following the inshore movement of spawning capelin, a primary food that gulls consume and feed to their chicks. Capelin availability occurred considerably later in 1997, when gull predation on storm-petrels was greater and prolonged. The intensity of gull predation on storm-petrels appears to depend on the availability of spawning capelin inshore.

Effects of Circadian Rhythm and Breeding Stage on Resting Metabolic Rates in Fasting Leach's Storm-petrels.

The oxygen consumption of fasting Leach's Storm-petrels Oceanodroma leucorhoa was measured in captivity with a metabolic chamber at nest burrow temperature (16°C). The average mass-specific oxygen consumption of incubating birds (2.84ml/g/h at night and 2.10ml/g/h in day) was lower than that of chick rearing birds (3.31ml/g/h at night and 2.98ml/g/h in day). Three days of fasting did not affect mass-specific oxygen consumption. At each breeding stage mass-specific oxygen consumption was higher at night than during the day (1.1-1.3 times). In the wild, body mass of incubating birds (45.7±2.9 SDg) was greater than those rearing chicks (43.1±2.7 SDg). It appeared that incubating birds may tolerate fasting for the 3 day incubation spell by reducing resting metabolic rate and spending metabolic energy on body fat reserves.

Heterosexual response to playback calls of the Leach's Storm-Petrel Oceanodroma leucorhoa.

Four calls of the Leach's Storm-Petrel (Oceanodroma leucorhoa), the Chatter-calls and Purr-calls of both sexes, were played back from a loudspeaker on the ground near the colony in Daikoku Island. All the playback calls attracted birds in flight and elicited Chatter-calls from them. The sex of the attracted birds were judged by analyzing the Chatter-calls. Significantly more birds responded to the playback call of the opposite sex than that of the same sex. It has already been revealed that birds inside burrows respond only to the playback calls of the same sex. Therefore, in this study it was found that the same call can elicit responses from different sexes in different circumstances. Thus, the same call can have different meanings in different contexts.

Regional difference in the diet of slaty-backed gulls breeding around Hokkaido.

Regional difference in the diet of Slaty-backed Gulls, Larus schistisagus was studied at the colonies around Hokkaido, Japan. They fed their chicks with sardines Sardinops melanosticta, rock fish Sebastes spp., and seabird chicks on Teuri Island, sardines on Daikoku Island and sardines and sandlances Ammodytes sp. on Yururi Island. They preyed upon chicks of seabirds such as Black-tailed Gulls L. crassirostris, Rhinoceros Auklets Cerorhinca monocerata and conspecifics on Teuri Island, while they preyed upon adults of Leach's Storm-Petrels Oceanodroma leucorhoa on Daikoku, Yururi and Moyururi Islands. Although availability of conspecific chicks was higher on Daikoku, Yururi and Moyururi Islands than on Teuri Island, they preyed upon conspecific chicks more frequently on Teuri Island than on Daikoku, Yururi and Moyururi Islands. Thus, availability of conspecific chicks did not explain the regional difference in the occurrence of predition attempts on conspecific chicks.