Main Breeding Season Research Articles

Climate change may account for the decline in British ring ouzels Turdus torquatus

1. Climate change is already affecting biodiversity, but the number of species for which reliable models relate weather and climate to demographic parameters is low. 2. We modelled the effect of temperature and rainfall on the breeding success and territory occupancy of ring ouzels Turdus torquatus (L.) in northern Britain, using data from a range of study areas, including one where there was a long-term decline in ring ouzel abundance. 3. Timing of breeding was significantly related to meteorological variables affecting birds in the early spring, though there was no evidence that laying dates had advanced. Breeding success was not significantly related to weather variables; instead, over 90% of annual variation in this parameter could be explained by density dependence. 4. Annual change in territory occupancy was linked to rainfall and temperature the preceding summer, after the main breeding season and to rainfall in the wintering grounds 24 months previously, coincident with the period of juniper Juniperus sp. (L.) flowering. High temperature in late summer, intermediate levels of late summer rainfall, and high spring rainfall in Morocco 24 months previously all had negative impacts on territory occupancy the following year. 5. All three weather variables have changed over recent decades, with a significant increase in summer temperature, a significant decrease in summer rainfall, and a nonsignificant decline in Moroccan spring rainfall. A model based on these trends alone predicted an annual decline in occupancy of 3.6% (compared with an observed decline of 1.2%), and suggested that increased summer temperatures may underlie declines in the British ring ouzel population. 6. Changes in summer temperature after the main breeding period could affect the survival rates of adult and/or juvenile birds. An improved understanding of the post-breeding ecology of ring ouzels is required to elucidate the mechanisms and causes of this relationship. Such knowledge might allow management aimed at buffering the impacts of climate change on ring ouzels.

Size at onset of maturity of spiny lobsters Panulirus homarus homarus at Mambrui, Kenya

The size at onset of sexual maturity of the scalloped spiny lobster Panulirus homarus homarus captured off Mambrui, Kenya, was estimated from ovary condition, presence of external eggs and/or spermatophore remains (berry method), and presence of well developed ovigerous setae (setal method). The predictive utility of morphometric relationships between carapace length (CL), pleopodal exopodite length (exopod length) and second leg length were assessed by fitting linear regressions to lobsters categorised as immature and mature, and comparing the intersect values with other estimates of functional maturity. The smallest female with mature ovaries was 52mm CL, compared with the smallest specimens of 50mm with ovigerous setae and 54mm with external eggs. Logistic curves indicated that 50% maturity was reached at 52.6mm (setal method) or 63.4mm (berry method) during the main breeding season. Female exopod lengths suggested that functional maturity was reached at 50.5mm and male leg lengths increased significantly upon reaching 57.5mm. The analyses indicate that measurements of female exopods and male second leg length can be used as cost-effective methods to estimate size at functional maturity of P. homarus homarus in Kenyan waters, and that these indices can augment estimates based on the presence of external eggs and ovigerous setae.

Reproduction and population dynamics of Leptochela gracilis (Decapoda: Pasiphaeidae) on the western coast of Korea, Yellow Sea

Investigations were made on reproduction and population dynamics of Leptochela gracilis on the western coast of Korea, Yellow Sea, between May 2000 and October 2001. The egg volume was significantly larger at later egg stage than at early egg stage. Brood loss did not occur during the incubation period. Based on dry weight, the reproductive output (mass of incubating eggs/mass of female) averaged 0.18. The mature females first appeared in May, reached a peak in July and August, and then did not appear after September. The main breeding season was summer, although slightly different between the two years. A similar pattern could be found in monthly changes of gonadosomatic index (GSI), showing relatively higher GSI during the annual breeding season. A significant difference in ovarian dry weight between females with non-eyed eggs and eyed eggs indicates that ovarian maturation occurred during the embryonic development, suggesting that females were potentially consecutive breeders, capable of multiple spawning within a reproductive season. The size at which 50% of females were mature (CL50) was estimated as 7.63 mm carapace length. Females grew faster and reached a larger size at age than males (L∞=12.43 mm CL and K=0.90 y−1 for females, and L∞=12.22 mm CL and K=0.58 y−1 for males).

Population dynamics of Rattus argentiventer, Rattus losea, and Rattus rattus inhabiting a mixed‐farming system in the Red River Delta, Vietnam

AbstractRodent pests cause significant damage to lowland irrigated rice crops in the Red River Delta of northern Vietnam. Data from a 4‐year study were examined to look at the population dynamics of the ricefield rat, Rattus argentiventer (representing 50% of captures), the lesser ricefield rat, Rattus losea (30% of captures), and the black rat, Rattusrattus complex (9% of captures) that inhabit the irrigated mixed‐cropping system. We tested the hypothesis that these rodent species were breeding in response to the availability of high‐quality food provided by crops rather than in response to rainfall. The abundance of rodents fluctuated annually, with a main peak following the spring rice crop, and a secondary peak following the summer rice crop. There was a strong relationship between the monthly abundance of rats and rainfall, but a weak relationship between monthly rates of increase and rainfall. There were distinct peaks in breeding activity during the reproductive stages of the rice crops suggesting that changes in crop stages were more important than rainfall in this seasonal, but irrigated agroecosystem. The modal litter size for R. argentiventer was 8 (mean of 8.67±0.20 SE, range 2–16), where the mode for R. losea, was 7 (mean of 7.32±0.15 SE, range 3–14). Management of these species needs to be conducted prior to the onset of the main breeding seasons.

The reintroduction, and subsequent impact, of rabbit haemorrhagic disease virus in a population of wild rabbits in south-western Australia

The natural arrival of rabbit haemorrhagic disease virus (RHDV) in south-western Australia in September 1996 resulted in a reduction in rabbit numbers of ~65% (~90% morbidity, with ~72% mortality of infected rabbits). As no signs of the disease (clinical or serological) were seen over the next two years, and as rabbit numbers over the last 12-month monitoring period at the site were similar to those observed before the natural 1996 RHDV epizootic (i.e. pre-RHD), RHDV was deliberately reintroduced into this rabbit population in April 1999 (autumn). Seven RHDV-inoculated rabbits were released prior to the main breeding season when <3% of sampled rabbits (n = 118) were seropositive for RHDV antibodies. Following the deliberate release, the overall decline in rabbit numbers (68%) was comparable to that seen during the natural 1996 epizootic. However, on the basis of the observed changes in rabbit numbers, and in their serology, the impact of the deliberate RHDV release appeared to be more variable across the six trapping areas than was seen during the natural 1996 spring epizootic. The reductions in rabbit numbers on these areas 6–8 weeks after RHDV-release ranged from 55% to 90%. The serology of the surviving rabbits on the trapping areas was also variable over this period, with the proportion of seropositive rabbits ranging from 5% to 90%. Overall, only 15% of the surviving rabbit population showed evidence of recent challenge by RHDV, giving a morbidity rate of 73% 8 weeks after the release. However, over 90% of infected rabbits died. This provides further evidence that some rabbits remained un-challenged by RHDV for up to 8 weeks after its release. The variable impact of the April 1999 release may have been partially caused by the observed differences in abundance of insect vectors, and/or an apparent increase in the incidence of non-virulent RHDV in the months preceding the release.

Reproductive biology of the common shrimp Crangon crangon (Decapoda: Crangonidae) in the central Irish Sea

Aspects of the reproductive biology of the common shrimp Crangon crangon (L.) were studied in Port Erin Bay, Isle of Man, Irish Sea. Size at sexual maturity was determined from the proportions of ovigerous females and of females with maturing ovaries. The size at which 50% of females are mature is estimated (±95% confidence intervals) as 12.5±0.48 mm carapace length. Based on the proportions of ovigerous females and of mature females, the main breeding season was from January to June. Mean ovarian dry weights indicated two broods (winter and summer), with females bearing winter broods (WB) having higher gonad indices than those with summer broods (SB). WB females with non-eyed eggs and with eyed eggs differed in the regression of ovarian dry weight on carapace length, indicating preparation for laying a second brood. In both broods the moult stages of berried females were related to egg stage. Moulting will occur following the release of the brood. During embryonic development, mean egg length and egg volume were larger in all stages, and the mean dry weight of individual eggs of all stages heavier, in WB than in SB; there was no difference in egg number, however. Consequently, reproductive investment, the proportion of female weight devoted to egg production, was 67% higher in WB (0.20±0.04) than in SB (0.12±0.03). There is a significant effect of egg volume on brood weight, but not on egg number. In both broods, egg number was a negatively allometric function of female body size in non-eyed eggs and an isometric function of female body size in eyed eggs. Brood mortality during incubation was higher in SB (17%) than WB (10%). Differences in the reproductive variables and investment between the two broods of C. crangon are discussed in the light of reproductive strategies and life history.

Reproduction and Population Dynamics of Acetes Chinensis (Decapoda: Sergestidae) on the Western Coast of Korea, Yellow Sea

Reproduction and population dynamics of Acetes chinensis were studied on the western coastal areas of Korea, Yellow Sea, between May 2000 and October 2001. Female maturity was determined from the ratios of females with maturing ovaries by size. The size at which 50% of females are mature is estimated as 8.96 mm carapace length. The mature females first appeared in April, reached a peak in July, and then did not appear after September. The main breeding season (percentage of females with mature ovaries greater than 50%) was from July to September. Similar pattern could be found in monthly changes of gonad index (GI), showing relatively higher GI during the annual breeding season. Mean gonad index examined weekly during the breeding season (June–September) peaked both in the middle of June and early September. Parameters of growth were estimated using the modified von Bertalanffy growth function (VBGF) model incorporating seasonal variation in growth. Females grew faster and reached a larger size at age than males (L∞ = 13.51 mm CL and K = 0.69 yr−1 for females, and L∞ = 10.48 mm CL and K = 0.84 yr−1 for males). The mortality rate (Z) (± 95% confidence limit) calculated by length-converted catch curves was estimated as 3.93 (± 2.00) yr−1. The structure of the recruitment patterns obtained by the ELEFAN program indicated two normally distributed groups. The estimated longevity was 0.75–1.0 yr for the summer generation and 0.58–0.83 yr for the winter generation.

Aspects of Breeding, Molt, Measurements and Population Trend of Hartlaub’s Gull in Western Cape, South Africa

Abstract In South Africa’s Western Cape, the main breeding season of Hartlaub’s Gull (Larus hartlaubii) is from January or February until May. At southern localities, there may be a second peak in breeding in August and September. Primary molt of adults mostly starts between August and December and lasts on average 115 days. In each of nine body measurements, averages were higher for males than for females, but values overlapped. In Western Cape during 1990-2001, the species bred at nine localities where breeding had not previously been reported. The maximum number recorded breeding at all localities in this region in any one year was about 5,500 pairs in 1995, less than the 10,000-11,000 pairs estimated for the region in the 1980s. Because the timing of the peak in breeding varies from year to year, it is considered that the 5,500 pairs represent an under-estimate, but it is likely that numbers did decrease after the 1980s. There are substantial inter-annual fluctuations in numbers of birds breeding, sug...

Fertility of dairy cows in Northern Ireland

A comprehensive database was established on the milk production and reproductive performance of dairy cows in 19 selected herds in Northern Ireland, varying in size, management system and genetic merit....

Pico- and nanoplankton from the inner Oslofjord, eastern Norway, including description of two new species of Luffisphaera (incerta sedis)

Species composition of pico- and nanoplanktonic flagellates in the inner Oslofjord was studied during the main breeding season of the blue mussel ( Mytilus edulis L.) in May-July. Light and electron microscopic studies on SDC (serial dilution cultures) and natural samples revealed the presence of more than 40 different photoautotrophic and heterotrophic taxa less than 10 µm in size. Two new species of the genus Luffisphaera are described: L. perforata and L. poculifera .

Relating the unique sensory system of amblypygids to the ecology and behavior ofPhrynus parvulusfrom Costa Rica (Arachnida, Amblypygi)

While the unique sensory system and neuroanatomy of amblypygids suggest that olfaction is important in their lives, to date no behavioral data exist to support this suggestion. To gain insight into amblypygid ecology and behavior, an individual mark–recapture study was conducted on the Costa Rican amblypygid Phrynus parvulus. Within two 50 by 25 m plots, the distribution and movement patterns of individual amblypygids were recorded for over 2 months. A total of 88 adult individuals (60 males and 28 females) were marked, with an average 51% resighted. Females were resighted more frequently than males (75% females, 40% males). The sexes did not differ in their frequency or movement distance, but females were more likely to be seen on the same tree over time. While both sexes potentially wander in search of mates, females may also be searching for a good crevice, or diurnal hideout. Once a female has mated and laid eggs, she likely remains stationary. Movement patterns and tree choice seem to be dictated by both the presence of conspecifics and environmental factors such as tree surface area, moss cover, and the presence of buttressing. Cumulative observational data collected over 3 years suggest that the main breeding season for this species is October-January. Both mate attraction and navigation may be facilitated by the olfactory capabilities of amblypygids, while their giant interneurons may be involved in their foraging behavior.

The Yellow‐necked Mouse Apodemus flavicollis in Britain: status and analysis of factors affecting distribution

ABSTRACTA national survey of the Yellow‐necked Mouse (Apodemus flavicollis) in Britain was undertaken by The Mammal Society. The live‐trapping study sampled small mammal populations from 168 deciduous woodlands in autumn 1998. Within their range, Yellow‐necked Mice were widespread in deciduous woodland and were more abundant than Wood Mice in 15% of the woodlands sampled. These trapping records, as well as records solicited from local recorders, record centres and individuals, supplemented the existing distribution map, confirming the general pattern, but with minor extensions to some range borders.Yellow‐necked Mice were found in woodland of all ages, but were more common in woods of ancient origin than in younger woodland. Woodland size was not important in determining the presence or abundance of Yellow‐necked Mice, but they were more often absent from woods more than 2 km from neighbouring substantial woodland.The presence of Yellow‐necked Mice did not affect the relative abundance of Wood Mice (Apodemus sylvaticus). However, the decline in the proportion of breeding male Wood Mice at the end of the main breeding season was more marked in those woods that also contained Yellow‐necked Mice. Where their ranges overlapped, Bank Voles (Clethrionomys glareolus) were less abundant where Yellow‐necked Mice were also present.The distribution of the Yellow‐necked Mouse was explored with respect to a number of climatic, soil and habitat variables. Maximum summer temperature was the most significant variable explaining distribution, although woodland cover variables also contributed. Soil moisture and pH, mean rainfall and winter temperature parameters did not predict Yellow‐necked Mouse distribution. Low summer temperature may limit Yellow‐necked Mouse distribution through its impact on tree seed production and diversity. Climatic change leading to a rise in summer temperature might encourage range expansion by Yellow‐necked Mice, if their other habitat requirements are met.

REPRODUCTION IN THE FRESH-WATER CRAB CANDIDIOPOTAMON RATHBUNAE (BRACHYURA: POTAMIDAE) IN TAIWAN

Abstract The reproductive biology of the Taiwanese fresh-water crab Candidiopotamon rathbunae (de Man) was investigated. The maturity, gonad development, mating behavior, breeding season, timing of release of young crabs, fecundity, and behavior of ovigerous females were studied. Mature males have sperm available for mating throughout the year. The deposition of yolk in females takes place mostly from April to June, with most of the eggs reaching maturity at the end of June. The main breeding season is from late June to October, although mating can occur all year round. In C. rathbunae, discernible courtship behavior is absent and a forced copulation strategy is practiced by males. Ovigerous females leave streams to live on the forest floor several meters away from the stream and are difficult to locate along the banks of streams. Ovigerous females return to the stream a few hours before hatching of the eggs. Most young crabs are released after mid-September, which is the end of the rainy season. This is ...

Reproduction in the Apodid Sea Cucumber Patinapta ooplax: Semilunar Spawning Cycle and Sex Change

Many fertile individuals of the apodid holothurian Patinata ooplax, living in the intertidal area of the Ichiki Fishing Port in southern Kyushu, Japan, spawned during the two days after every full and new moon, probably the first and second days, in the period from the middle of July to the end of August during 1990, 1992 and 1993. Matured individuals were divided into three sexual types: males, hermaphroditic males with an early stage of oocytes, and females, using a dissecting microscope. The distribution frequency and gonadal histology of these sexual types indicate that some individuals changed from male to female or in the reverse direction at two-week intervals between spawnings, and suggest that some change first from male to female, and then back to male during the main breeding season. In addition, it was found that during the main breeding season, synchronous gametogenesis occurred in association with the sex changes, and that the period from the initiation of spermatogonia proliferation to sperm release during the same season was two weeks, and the period from the initiation of oocyte growth to egg shedding was probably slightly longer than two weeks.

Reproduction in the Fresh-Water Crab Candidiopotamon Rathbunae (Brachyura: Potamidae) in Taiwan

The reproductive biology of the Taiwanese fresh-water crab Candidiopotamon rathbunae (de Man) was investigated. The maturity, gonad development, mating behavior, breeding season, timing of release of young crabs, fecundity, and behavior of ovigerous females were studied. Mature males have sperm available for mating throughout the year. The deposition of yolk in females takes place mostly from April to June, with most of the eggs reaching maturity at the end of June. The main breeding season is from late June to October, although mating can occur all year round. In C. rathbunae, discernible courtship behavior is absent and a forced copulation strategy is practiced by males. Ovigerous females leave streams to live on the forest floor several meters away from the stream and are difficult to locate along the banks of streams. Ovigerous females return to the stream a few hours before hatching of the eggs. Most young crabs are released after mid-September, which is the end of the rainy season. This is believed to be a strategy to avoid destructive flash floods which are common from mid-May to early September. The number of eggs carried by each ovigerous female ranges 9–117, fecundity being highest for females of about 30-mm carapace width.

Resource seasonality and the structure of mixed species bird flocks in a coastal Atlantic forest of southeastern Brazil

ABSTRACT. Multi-species bird flocks in tropical forests are maintained throughout the annual cycle despite seasonal differences in resource availability, and the reproductive schedules and ecological requirements of individual species. This study examines the relationship between seasonal variation in flock structure and the availability of fruits and arthropods over a 12-mo period at a coastal Atlantic forest within the Juréia–Itatins Ecological Station, São Paulo, Brazil. Fruit abundance was estimated by a phenological survey of both canopy and understory trees, whereas arthropod abundance was quantified monthly on the basis of a nocturnal visual census technique. The seasonal variation in flock structure and composition was affected by both the breeding seasons of different core and attendant species, and the availability of food resources. The number of bird species attending flocks was greater during the dry season, declining thereafter during the breeding season. Understorey fruit availability exhibited a marked seasonal fluctuation with the lowest levels between the late dry and early wet season. Seasonal variation in canopy fruit availability, on the other hand, was far less demarcated than that of understorey plants. Arthropod abundance was greatest during the wettest months of the year, which apparently determined the timing of the main breeding season. Bird species richness attending flocks was, therefore, significantly correlated with the availability of understorey arthropods, but not with that of either understorey and canopy fruits. Arthropod abundance thus appears to affect profoundly the reproductive schedules of the understorey avifauna, which in turn influences the seasonal variation of flock size and composition.RESUMO. Nas florestas tropicais a formação de bandos mistos de aves ocorre ao longo de todo o ano, porém existem variações sazonais na composição e estrutura destes bandos. Tais variações estão ligadas ao período reprodutivo das aves, à disponibilidade de recursos alimentares e a requisitos ecológicos inerentes a cada espécie. Este trabalho analisou a dinâmica sazonal destes bandos durante um ano, relacionando estes dados com a disponibilidade de recursos alimentares em uma área de Mata Atlântica na Estação Ecológica Juréia–Itatins. A disponibilidade de frutos foi estimada através de acompanhamento fenológico de espécies de dossel e de sub-bosque, enquanto a abundância de artrópodos foi feita através de censos noturnos mensais. A variação sazonal na estrutura e composição dos bandos foi afetada pela atividade reprodutiva das espécies mais freqüentes e pela disponibilidade de recursos alimentares. Nos meses mais secos ocorreu um aumento do número de espécies nos bandos, ocorrendo um declínio durante o período de reprodução das aves. A quantidade de frutos de sub-bosque apresentou maior escassez entre o final do período seco e o início do período chuvoso, variando de maneira muito mais drástica quando comparada aos frutos de dossel. A abundância de artrópodos foi maior durante os meses mais chuvosos do ano, coincidindo com a época reprodutiva das aves. A riqueza das espécies de aves associadas a bandos mistos foi significativamente correlacionada com a abundância de artrópodos, mas não com a disponibilidade de frutos de dossel e sub-bosque. A abundância de artrópodos deve ter influenciado o início das atividades reprodutivas das aves, que por sua vez, causou as variações sazonais na composição e tamanho dos bandos.

Seasonal pattern of breeding by Cape and Crowned Cormorants off western South Africa

Crawford, R.J.M., Dyer, B.M. & Upfold, L. 1999. Seasonal pattern of breeding by Cape and Crowned Cormorants off western South Africa. Ostrich 70(3&4): 193–195. At Bird Island, Lambert's Bay, and Malgas Island, South Africa, small numbers of Cape Cormorants Phalacrocorax capensis may breed at any time of the year, but the main breeding season is from September to February. At Malgas Island, Crowned Cormorants P. coronatus may also breed throughout the year, but mostly from December to March. Counts of the breeding population of Cape Cormorants should be undertaken between October and December, and of Crowned Cormorants in January or February.

Seasonality of a forest bird community in Hong Kong, South China

We studied the composition of a secondary forest bird community in Hong Kong (22°N) between December 1992 and June 1995, using the variable point count method. The visual detectability of each bird species had a significant positive relationship with body length. A total of 71 bird species was recorded but three resident habitat‐generalists, the Great Tit Parus major, Light‐vented Bulbul Pycnonotus sinensis and Japanese White‐eye Zosterops japonicus, accounted for 65% of the mean total bird density of 38 per ha. The number of species seen was highest between December and April and lowest from July to September, but the total bird density was highest between December and June and lowest from August to September. The main breeding season was from March to August. Insectivores and insectivore‐frugivores accounted for 80% of the species and 98% of the total bird density. The percentages of migrant species and individuals are similar to those reported at equivalent latitudes in North America. Bird community diversity and composition differed considerably from that of larger, older forest areas in South China, presumably as a result of differences in forest age, area and isolation.

Notes on breeding and conservation of birds on Niuafo'ou Island, Kingdom of Tonga

Niuafo'ou lies very isolated in the Pacific, is well forested and not densely populated by humans. These facts as well as the lack of larger rat species make it a refuge for birds rare elsewhere in the region. This paper covers all 17 breeding species and gives breeding data for 14 of them, collected from October 1991 to December 1992. Ten species had a well-defined breeding season of 2?7 months somewhere between September and April, which often differed from other adjacent islands: Audubon's Shearwater Puffinus Iherminieri, Pacific Black Duck Anas superciliosa, Banded Rail Rallus phillippensis, Spotless Crake Porzana tabuensis, Purple Swamphen Porphyrio porphyrio, Barn Owl Tyto alba, Red-vented Bulbul Pycnonotus cafer, Polynesian Starling Aplonis tabuensis nesiotes, and Jungle Myna Acridotheres fuscus. The Blue-crowned Lorikeet Vini australis nested in October, November and July. It did not only breed in tree hollows, but also inside a rotten log on the ground. Other observations suggest that it visits ground holes as well, either for nesting or resting. A breeding colony of Audubon's Shearwater is the first one confirmed for Tonga. Four species nested in the wet and dry season: White-tailed Tropicbird Phaethon lepturus, Pacific Reef-heron Egretta sacra, Pacific Pigeon Ducula pacifica and Polynesian Megapode Megapodius pritchardii. Since September to March is the main breeding season for birds on Niuafo'ou, it is proposed that hunting and egg collecting, both important parts of the local tradition, are restricted to the other months of the year. In case of the endangered Polynesian Megapode we suggest a restriction of egg collecting and propose a translocation programme to another island. Additionally, we suggest that the islets in the crater lake become protected as they are free of feral cats, and some birds occur in higher densities there. Niuafo'ou also deserves attention as resting place for six vagrant and migrant species; large numbers of Wedge-tailed Shearwaters Puffinus pacificus are hunted when they visit between October and June.

Seasonal pattern of breeding, population trend and conservation status of bank cormorants Phalacrocorax neglectus off south western Africa

At Robben and Malgas islands off western South Africa, the main breeding season for bank cormorants Phalacrocorax neglectus normally extends from May to October. At Ichaboe and Mercury islands, off central Namibia, most breeding activity is usually concentrated between November and April. The overall number of breeding pairs of bank cormorants fell from 8672 in 1978–80 to 4888 in 1995–1997. Human disturbance resulted in the loss of four colonies and reduced populations at six others. About 3000 pairs were lost from the Mercury and Ichaboe islands because of displacement of birds from Mercury Island by Cape fur seals Arctocephalus pusillus in the 1980s and a severe reduction in food off central Namibia in the 1990s. Competition with seals for space occurs at several other localities. Using IUCN criteria, the bank cormorant merits classification as `vulnerable'.