Burrow densities and nest site preferences of petrels (Procellariidae) at the Prince Edwards Islands

Summary The nest-site preferences of six burrowing petrel species, Salvin's prion Pachyptila vittata salvini, blue petrel Halobaena caerulea, great-winged petrel Pterodroma macroptera, Kerguelen petrel Pterodroma brevirostris, soft-plumaged petrel Pterodroma mollis and white-chinned petrel Procellaria aequinoctialis, in the northeastern part of Marion Island (Prince Edward Island group, southern Indian Ocean) were analyzed by step-wise multiple regression. The nest-site characteristics measured were slope angle, soil depth and moisture content, percentage cover by stones or boulders and percentage cover by each of seven major plant species. The major nest-site preferences were: exposed areas with shallow soil (Salvin's prion); steep coastal slopes (blue petrel); sheltered well-drained slopes with deep soil (great-winged petrels); wet areas along drainage lines (Kerguelen petrel); steep slopes (soft-plumaged petrel); and areas with deep soil (white-chinned petrel). Similar species showed no significant avoidance of nest sites where there were burrows of potential competitors but did tend to nest spread out over different habitats. Burrow densities were determined in six habitat and seven vegetation types. Salvin's prion was the most abundant species (81% of burrows, with a maximum density of 279 burrows ha^-1) and used both burrows and natural cavities for nesting. For all species combined, burrow densities at Marion Island were lower than in comparable habitats and vegetation types at neighbouring Prince Edward Island. Depredation by feral house cats Felis catus, absent from Prince Edward Island, is assumed to be largely responsible for this difference.     

An assessment of the breeding range,colony sizes and population of the Westland petrel (Procellaria westlandica)

Abstract

The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs.     

Diving behaviour of white-chinned petrels and its relevance for mitigating longline bycatch

The white-chinned petrel (Procellaria aequinoctialis) is the seabird species most commonly killed by Southern Hemisphere longline fisheries. Despite the importance of diving ability for mitigating longline bycatch, little is known of this species’ diving behaviour. We obtained data from temperature–depth recorders from nine white-chinned petrels breeding on Marion Island, southwestern Indian Ocean, during the late incubation and chick-rearing period. Maximum dive depth (16 m) was slightly deeper than the previous estimate (13 m), but varied considerably among individuals (range 2–16 m). Males dived deeper than females, and birds feeding chicks dived deeper than incubating birds, but dive rate did not differ between the sexes. Time of day had no significant effect on dive depth or rate. Our findings will help to improve the design and performance of mitigation measures aimed at reducing seabird bycatch in longline fisheries, such as the calculation of minimum line sink rates and optimum aerial coverage of bird-scaring lines.     

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.     

The fern genus Elaphoglossum section Lepidoglossa (Dryopteridaceae) in Africa,Macaronesia, the mid‐Atlantic and southern Indian Ocean Islands

Elaphoglossum section Lepidoglossa in Africa, Macaronesia (Azores and Madeira), the mid‐Atlantic Ocean Islands (St Helena, Gough and Tristan da Cunha Island groups) and the southern Indian Ocean Islands (Marion and Prince Edward Islands) is reviewed. Fifteen Elaphoglossum species from this region are ascribed to the section. A new species, Elaphoglossum rivularum , confined to the Chimanimani Mountains in eastern Zimbabwe and formerly ascribed to E. kuhnii from West Africa, is described. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 20–63.     

New records of alien vascular plants from Marion and Prince Edward Islands, sub-Antarctic

A survey was made of the distribution of introduced vascular plants on Marion and Prince Edward Islands. The results of this survey were compared to results of previous surveys (1965/66, 1975, 1981, 1989). Four new introductions to Marion Island have taken place, three of which involved species that had been introduced in the past, but had disappeared or were eradicated. Eighteen species of alien vascular plants are now known from Marion Island. Of these, three were not observed during the present survey, and another three have been eradicated. Many of the naturalised aliens are still increasing markedly in area and/or in numbers. Rates of spread of up to 300 m year⁻¹ occur. Three alien vascular species occur on Prince Edward Island. Two are recent introductions, presumably transported to this island from neighbouring Marion Island by wind or birds. Accepted: 22 November 1998     

Diatom communities from the sub-Antarctic Prince Edward Islands: diversity and distribution patterns

During an extensive survey of the freshwater and moss-inhabiting diatoms of the Prince Edward Islands, a total of 214 taxa belonging to 60 genera were found. Three main communities can be found on the two islands. A large part of the samples was grouped into an aquatic group, bringing together all samples from lentic and lotic waterbodies. A second, contrasting, group was formed by all dry samples whereas in a third group all habitats with higher mineral contents were found. The habitats differed clearly in taxa composition reflecting that way possible environmental differences. Although the diatom composition between the two islands of this island group (Marion and Prince Edward Island) showed some minor qualitative differences, no marked quantitative differences have been observed. The diatom flora shows a distinct similarity with the other islands in the southern Indian Ocean, such as the Crozet archipelago and the Kerguelen Islands forming a biogeographical entity in this part of the ocean, distinctly separated from the non-marine diatom flora in other parts of the (sub-)Antarctic Region.     

New records of Acari from the sub-Antarctic Prince Edward Islands

Sixty species of Acari are recorded from the sub-Antarctic Marion and Prince Edward Islands (the Prince Edward archipelago). Twenty of the 45 species collected on recent expeditions are new and currently undescribed. Other new taxa include a family of Mesostigmata, four new genera, and the first sub-Antarctic records of Cillibidae (Mesostigmata) and Eryngiopus (Prostigmata). Fifteen of the 31 species previously reported from the islands are confirmed, although eight of the previous accounts remain doubtful. The fauna, which shows a distinction between the shoreline and terrestrial components, comprises endemic, South Indian Ocean Province and sub-Antarctic mite species. Accepted: 18 July 1998     

Climate change and the short-term impact of feral house mice at the sub-Antarctic Prince Edward Islands

At the Prince Edward Islands, temperatures have increased by approximately 1°C over the past 40 years, accompanied by a decline in precipitation. This has led to a reduction in the peat moisture content of mires and higher growing season warmth. The temperature-and moisture-sensitive sedge, Uncinia compacta R. Br. (Cyperaceae), has consequently increased its aerial cover on Prince Edward Island, but harvesting of seeds by feral house mice (up to 100% removed) has prevented this from happening on Marion Island. Such extensive use of resources suggests that prey switching may be taking place at Marion Island. Scat analyses revealed that mice are·not only eating ectemnorhinine weevils to a greater extent than found in previous studies of populations at Marion Island, but that they also prefer larger weevils (±6 mm). A decrease in body size of preferred weevil prey species [Bothrometopus randi Jeannel and Ectemnorhinus similis C.O. Waterhouse (Coleoptera: Curculionidae)] has taken place on Marion Island (1986–1992), but not on Prince Edward Island. This appears to be a result of increased predation on weevils. In addition, adults of the prey species, E. similis are relatively more abundant on Prince Edward Island than adults of the smaller congener E. marioni Jeannel, and could not be found on Marion Island in the late austral summer of 1991. These results not only provide support for previous hypotheses of the effect of global warming on mouse-plant-invertebrate interactions on the Prince Edward Islands, but also provide limited evidence for the first recorded case of predator-mediated speciation. They also show that the interaction of human-induced changes operating at different scales may have profound consequences for local systems.     

Insular bird populations can be saved from rats: a long-term experimental study of white-chinned petrels<Emphasis Type="Italic"> Procellaria aequinoctialis</Emphasis> on Ile de la Possession (Crozet archipelago)

The white-chinned petrel is a subantarctic seabird that requires urgent implementation of conservation measures for the species. At sea, adults suffer heavy mortality due to fisheries' practices. On land, introduced rats prey on chicks at several localities, and we test here if and how rats can be efficiently controlled. Since 1994, we have conducted an intensive rat-control program during each breeding season in a white-chinned petrel colony on Ile de la Possession (150 km²; Crozet archipelago, southern Indian Ocean), which had been monitored since 1986. On the same island, a control white-chinned petrel colony, where no poisoning occurred, was also monitored, and we assessed the seasonal variations of rat abundance. We compared three situations: high rat-poisoning, low rat-poisoning and control conditions without poisoning. Low-poisoning trials performed in our experimental colony between 1988 and 1991 did not lead to higher chick production than for the previous two control years. However, petrel-breeding success was significantly higher when intensive poisoning occurred (50%) than for the previous years (16%). The duration of our study (8 years before intensive poisoning, plus 8 years afterwards), combined with a comparison of petrel annual breeding success between our experimental and control colonies, allowed us to assess more effectively the impact of rats. Forty-one per cent of breeding failures occurring in non-poisoned areas were attributed to rats. We conclude that threatened insular bird populations can be conserved and restored in localities even where total rat eradication is not possible. However, only intensive and repeated (long-term) poisoning will control rats sufficiently.     

Differences in habitat selection between Chatham petrels (

The Chatham petrel (Pterodroma axillaris) is an endangered species restricted to a single population on South East Island, Chatham Islands, New Zealand. The key threat to Chatham petrel breeding success is interference with chicks by broad-billed prions (Pachyptila vittata) prospecting for burrows for their oncoming breeding season. This burrow competition has resulted from alteration to breeding habitat by humans throughout the Chatham Islands. Understanding habitat preferences may enable managers to manipulate habitat to reduce burrow competition and will be essential in order to translocate Chatham petrels to a proposed second colony. Habitat characteristics surrounding both Chatham petrel and broad-billed prion burrows were quantified and selection ratios compared. Both Chatham petrels and broad-billed prions selected habitat factors associated with mature forest. Chatham petrels avoided a large number of habitat characteristics, which suggests they were habitat specific, and their preferred habitat is now limited. Broad- billed prions used a wide range of habitat characteristics, which suggests they are not habitat specific. This study recommends that selection values be used when deciding on the best location to establish a second Chatham petrel colony.     

Use of burrow entrance flaps to minimise interference to Chatham petrel (

The Chatham petrel (Pterodroma axillaris) is an endangered species, restricted to a single population on South East Island, Chatham Islands. The key threat to breeding success is loss of chicks as a result of interference by broad-billed prions (Pachyptila vittata) prospecting for burrows for their oncoming breeding season. The effectiveness in decreasing interference using an artificial burrow entrance flap was investigated. The flap exploits behavioural differences between the species. Chatham petrels have a high incentive to push through a flap due to their investment in their burrow and chick, while prospecting prions are influenced by ease of access when searching for potential burrows. This trial found 90% of Chatham petrels entered their burrows through the artificial flap. Flaps acted as barriers to broad-billed prions, where 22% entered the burrow through the flap (P <0.01) compared to the control burrows. Artificial burrow flaps have the potential to provide a low cost, low labour strategy for protecting the known breeding population of Chatham petrels.     

The vocal systems of two nocturnal burrowing petrels, the White-chinned Procellaria aequinoctialis and the Grey P. cinerea

I studied the calls of White-chinned Petrels Procellaria aequinoctialis and Grey Petrels P. cinerea at the Prince Edward Islands in the Southern Ocean. White-chinned Petrels gave two calls. One, the Wheezy call, was usually given from within breeding burrows, was given in response to playback of strange (= non-mate) calls, and probably served a burrow defence function. The other call, the Rattle call, was uttered roughly as often on the ground as from within the burrow. This call was mostly given by males and probably served as sexual advertisement. The one identified call type of the Grey Petrel was given in the same circumstances as the Wheezy call of the White-chinned Petrel.
In both species there was evidence of mate recognition of calls. Birds tended to remain silent to the playback of the mate's call, whereas they responded vocally to strange calls.
This vocal system, where both sexes share two call types but where sexual dimorphism in call is absent, has not been described before for petrels. Possible reasons for the variation in petrel vocal systems are discussed.     

Breeding frequency in Grey-headed Albatrosses Thalassarche chrysostoma

Although Grey-headed Albatrosses Thalassarche chrysostoma are usually regarded as biennial breeders, taking a year off following a successful breeding attempt, a small proportion of successful birds attempt to breed annually. This proportion was higher at Marion Island (5.4%) than at Bird Island, South Georgia (1.0%), suggesting that conditions are more favourable at Marion Island. This hypothesis is supported by higher average breeding success and shorter lags following both successful and failed breeding attempts at Marion Island. Factors favouring reproduction at Marion Island may include reduced intraspecific competition (given the much smaller breeding population) and/or more predictable food supply (owing to production of meso-scale eddies associated with the Indian Ocean Ridge). Although annual breeding appeared to increase the risk of adult mortality, with several birds that attempted to breed annually found dead the following year, at least some birds greatly enhanced their reproductive output, with one male raising five chicks in five successive years. Contrary to life-history theory, there was no evidence that older birds were more likely to attempt annual breeding because of declining reproductive value.     

Killer whale predation on subantarctic fur seals at Prince Edward Island, Southern Indian Ocean

Killer whales at subantarctic Marion Island have been subjected to several scientific studies. In contrast, up until recently, there has been only one record of these animals documented for neighbouring Prince Edward Island. We here report on killer whale observations at Prince Edward Island during March 2012. During 3?days of opportunistic observations at a fur seal colony on the island, killer whales were sighted on six occasions. These probably represented three different pods numbering 11 individuals in total. During all sightings, individuals were seen hunting subantarctic fur seal pups, with four successful predatory events observed.     

MOVEMENTS OF SOUTHERN ELEPHANT SEALS AND SUBANTARCTIC FUR SEALS IN RELATION TO MARION ISLAND

Based primarily on an intensive marking/resighting program conducted at Marion Island (46°54'S, 37°45'E) in the Southern Ocean, the inter-island movements of southern elephant seals, Mirounga leonina , and fur seals Arctocephalus spp., were investigated to elucidate their little known pelagic phase. Southern elephant seals, in particular immature animals, readily move between the proximate Marion and Prince Edward islands. Some range as far afield as Iles Crozet, approximately 1,000 km distant where they haul out for the summer molt or during an autumn resting phase. The exchange of individuals between Marion Island and Iles Crozet during the return of immatures for the molt after a winter at sea, suggests overlapping of the foraging ranges of the two populations. Despite their wanderings, the majority of M. leonina from Marion Island probably feed in the proximity of the island, and relocate onto the island for breeding, molting and resting. Of the fur seals, only a few A. tropicalis were seen away from their natal island, in some cases covering distances in excess of 2,000 km. displaying a remarkable dispersal capacity.     

The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls

This paper reports the breeding biology and nesting seasons of the gadfly petrels which nest on the four islands of the Pitcairn group, Pitcairn, Henderson, Oeno and Ducie. The species currently breeding are Murphy's petrel Pterodroma ultima , Kermadec petrel P. neglecta , Herald petrel P. heraldica and Henderson petrel P. atrata. Of these, Murphy's petrel is the most numerous; an estimated 250000 pairs bred on Ducie, which is probably the major breeding station of the species. Novel basic breeding data for Murphy's petrel are presented. Incubation spells, averaging 19.3 days, are exceptionally long for a petrel. Phoenix petrel P. alba appears to have ceased to breed on the Pitcairn Islands since the 1922 surveys of the Whitney Expedition. Nesting success was low on Henderson Island during the study. For all four breeding species, less than 20% of eggs laid yielded fledglings. Failure occurred at the early chick stage and observations indicated that it was due to predation by Pacific rats Rattus exulans. Although rats are present on Ducie, predation was apparently less severe there. The situation on Oeno may be intermediate. I consider how the populations of Henderson are maintained in the face of this intense predation. The Murphy's petrel population may be sustained by immigration from Ducie while the Herald and Henderson petrel populations could be undergoing a long-term decline on Henderson. It is not clear how the Kermadec petrel population is maintained. The conservation implications of these findings are discussed.     

Long distance breeding dispersal of a southern elephant seal

Southern elephant seals range extensively during regular foraging excursions. Despite this they are highly philopatric and long range dispersal is rare. At Gough Island, southern Atlantic Ocean, we observed a breeding adult male elephant seal during September 2009, which had been tagged on its natal beach at Marion Island, southern Indian Ocean, in November 1998. The individual was resighted only once on Marion Island, 6 months after tagging. This 3,860 km movement represents dispersal (and likely gene flow) between distinct populations from different elephant seal geographical provinces. Given the polygynous breeding system of this species, the presence of this single male may have a disproportionate genetic effect on the small number of southern elephant seals breeding at Gough Island.     

The white-chinned petrel (<Emphasis Type="Italic">Procellaria aequinoctialis</Emphasis>) on South Georgia: population size,distribution and global significance

More white-chinned petrels (Procellaria aequinoctialis) are accidentally killed in fisheries than probably any other seabird in the world, but the population impact of this mortality is poorly understood, partly because there have been no recent estimates of the species’ abundance. The breeding aggregation on the sub-Antarctic island of South Georgia is believed to be larger than all others combined. We estimated the size of this population by calculating the area of suitable habitat and the density of occupied burrows within it. Some 670,000 occupied nests were estimated for the island at mid-incubation, representing 0.9 million pairs of breeding-age birds associated with South Georgia in the survey seasons (2005/06 and 06/07). This is 40–45% of the previous estimate, but still represents well over half of the global population. If the population is declining due to fishery bycatch, as is likely, the scale of annual mortality in this population alone is at least in the high tens of thousands, and plausibly hundreds of thousands.