Colony attendance and censusing of Black Guillemots Cepphus grylle in Shetland

The diurnal rhythm of colony attendance by Black Guillemots varied seasonally. No tidal effects were detected but in April attendance was lower when winds exceeded force 4. Numbers were most stable during 05.00–08.00 GMT in the pre-breeding period. Counts at this time and in winds of force 4 or less provide the best estimate of adult populations. Between late March and mid-May, counts of adults associated with breeding habitat account for most birds occupying suitable nest sites and censuses in northern Britain should be conducted in this period. As the proportion of non-breeding adults varies between colonies, no universal correction factor can be used to estimate the number of breeding attempts from counts of birds. Counts aimed at detecting maximum attendance provide greater accuracy than single counts made by flushing all birds on to the sea but take longer. Monitoring units should be stretches o-f coastline that include a number of colonies of different sizes.     

The diet of black guillemots Cepphus grylle in Shetland

The diet of black guillemots Cepphus grylle (L.) was studied in Shetland between 1982 and 1985, both during and outside the breeding season. Full-grown birds consumed a wide variety of fish and invertebrate species in summer, broadly reflecting the diversity of the inshore benthic fauna. In winter a greater diversity of invertebrates was taken, which assumed increased importance in the diet as the availability of benthic fish probably declined. Chicks were fed a diet of fish, with 70–80% being sandeels Ammodytes marinus and butterfish Pholis gunnellus on the island of Mousa. Sandeels were delivered more frequently in the early morning, coincident with a peak in their feeding activity. Older chicks were fed significantly longer fish. The composition of chick diet varied significantly with date, not chick age. A seasonal decline in the proportion of sandeels in the chick diet may have reflected changes in Zooplankton abundance, but the possibility that intensive industrial fishing of sandeels had adversely affected local stocks can not be ruled out.     

The breeding biology of Guillemots Uria aalge on the Isle of May over a six year period

The breeding of Guillemots was studied in five areas of different breeding density and habitat type on the Isle of May in 1981-86. Prior to 1981 numbers were increasing at 5 6° per annum but during the study the rate of increase slowed down and from 1983 to 1986 numbers were fairly constant. Adult survival was high, with a mean minimum annual adult survival of 930% (s.e. = 03). Observations in 1986 suggested that the percentage return of colour-marked immature birds was low, with only l-6% and 5.5% of second and third year birds being seen. We suggest that poor recruitment was responsible for the levelling off in numbers at the colony.
The timing of laying was constant from year to year in 1981-85 but was later in 1986. It was significantly and inversely related to sea temperature the previous March. There was a consistent ranking in median laying dates amongst the areas, with area 1 (the highest density of birds) always earliest. However, there was no significant difference in synchrony between the areas. Overall breeding success was high (0–71-0-82 young fledged per pair). There was no consistent ranking of breeding success with breeding density, habitat type or laying synchrony.
The only aspect of Guillemot biology which changed significantly was the daily food intake of a chick which approximately halved during the study period. However, this reduction in food intake had no detectable effect on either the weight of chicks with wing lengths greater than 60 mm or the amount of time off-duty breeders spent at the site. Both of these parameters were still consistent with conditions being favourable in 1986.     

Effects of short-term hunger and competitive asymmetry on facultative aggression in nestling black guillemots Cepphus grylle

Siblings in a diversity of species are facultatively aggressive,yet the proximate control of the aggressive response and theecological conditions selecting for such systems are poorlyunderstood. In this study, we investigated the effects of foodamount (food amount hypothesis) and competitive asymmetry onsibling aggression in black guillemot broods. Parental provisioningrates were experimentally manipulated in broods comprisinga range of hatching intervals over a 12-h period. Aggressionbecame evident only after parental provisioning rates wereexperimentally reduced. When parental provisioning resumed,adults did not increase their feeding rate to compensate forthe induced food deficit, and the result of sibling rivalrywas a change in the allocation of parental deliveries from oneof equality to one in favor of the dominant chick. Food-deprivedchicks from synchronous broods were more aggressive than thosefrom asynchronous broods, suggesting that one benefit of hatchingasynchrony in the black guillemot is to establish an efficientcompetitive hierarchy among siblings which minimizes the needfor costly aggressive interactions. On the following day, siblingaggression ceased, and chicks regained an equal share of parentalfeeds. Our results provide the first evidence that short-termfood shortage per se acts as an initial trigger for aggressionand also show that the aggressive response is complicated byfactors associated with hatching and laying order.     

The effects of food abundance on breeding performance and adult time budgets of Guillemots Uria aalge

The breeding performance, food fed to chicks and adult time budgets of Guillemots Uria aalge were examined in a year of high and a year of low food availabiIity. There was no difference between the 2 years in reproductive success, although the rate of chick feeding, chick weight and fledging success were greater in the year of high food availability. On average, chick prey items were larger in the poor food year, but this was insufficient to compensate for the lower feeding frequency. Chick feeding frequency did not differ between days in the good year but did increase later in the season in the poor food year. Compared with the high food availability year, adult Guillemots in the year of low food availability spent much less time resting at the breeding colony. and their foraging trips were twice as long. Foraging birds tended to make several successive trips before resuming brooding duties from their mates when food supplies were good, but in the low food availability year single trips were the norm. These results demonstrate that predators experiencing reduced food supply may mitigate the effects on their reproductive output by shifting their time allocation such that more time is available for foraging.     

The breeding biology of the Scimitarbilled Woodhoopoe

Steyn, P. 1999. The breeding biology of the Scimitarbilled Woodhoopoe. Ostrich 70 (3&4): 173–178.

The breeding biology of the Scimitarbilled Woodhoopoe Rhinopomastus cyanomelas was studied at two sites in Zimbabwe over a 13-year period from 1964–1977. The pairs were resident, remained together throughout the year, and inspected their nest sites occasionally during the non-breeding season. The breeding season extended from August to December with a marked September/October peak. Eggs were laid at daily intervals. Clutch size averaged 2.9 (range 2–4). Incubation began either with the penultimate or last laid egg. During the 13–14 day incubation period the female left the nest only occasionally each day and was reliant on the male for food. This pattern continued for four days after the chicks hatch. Thereafter she started to forage and gradually increased her contribution to chick provisioning until she overtook that of the male. With one exception, he never fed the chicks directly and delivered the food to the female. The nestlings were brooded overnight for the first two weeks. The anti-predator response of the young included a malodorous brown exudation from the preen gland and unpleasant liquid excreta. The nestling period was 21–24 days and the young left the vicinity of the nest with their parents and did not return to roost in it. Twelve breeding cycles were monitored and 76% of eggs laid (n=37) produced fledged young. Second broods were raised in the same nest on two occasions after successful rearing of the first, presumably by the same pair, but the birds were not individually marked. There was no evidence of helpers at the nest.     

The influence of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in Shetland

We measured the breeding performance, body condition, time budgets and foraging ranges of Kittiwakes Rissa tridactyla at Sumburgh Head, Shetland, in two years of contrasting food availability. Kittiwakes in Shetland generally feed their young almost entirely on sandeels, and fisheries data indicated that stocks of sandeels in Shetland waters were at least ten times higher in 1991 than in 1990. Fledging success of Kittiwakes was nil in 1990 and 68% of eggs laid in 1991, although clutch-size and hatching success were no different between years. Post-hatching foraging trips in 1991 were of comparable duration to those recorded at other colonies in conditions of good food supply (2–3 h), while trips recorded during incubation or post-hatching in 1990 were approximately three times longer on average than at corresponding stages of the breeding season in 1991. Radio-tracking data indicated that adults generally stayed within 5 km of the colony in 1991 but flew more than 40 km from the colony on each trip in 1990. Eggs were apparently not left unattended in either year, despite the fact that this required adults to incubate for periods in excess of 44 h in 1990. The extent to which adults were able to increase trip durations, foraging ranges and incubation shift lengths between years, while maintaining hatching success, indicates the degree to which Kittiwakes are normally buffered against adverse feeding conditions during incubation. Reduced nest attendance and lower body-condition of adults post-hatching in 1990, in conjunction with complete post-hatching breeding failure, indicate that adults were beyond the limits of their buffering capacity during chick-rearing in 1990.     

Variation in the correction factor used for converting counts of individual Guillemots Uria aalge into breeding pairs

The correction factor k (breeding pairs/total count of birds) was measured for two nesting groups of Guillemots Uria aalge over 6–7 years. The value varied between different subgroups but there were no significant differences between groups or between years. These results, and those from other studies, suggest that a value of 0–67 is applicable to a range of colonies. Values of k for Razorbills Aha tarda were more variable. A plea is made for the presentation of original counts rather than 'corrected' figures in published work.     

Variance in prey abundance influences time budgets of breeding seabirds: evidence from pigeon guillemots Cepphus columba

We use data on pigeon guillemots Cepphus columba to test the hypothesis that discretionary time in breeding seabirds is correlated with variance in prey abundance. We measured the amount of time that guillemots spent at the colony before delivering fish to chicks ("resting time") in relation to fish abundance as measured by beach seines and bottom trawls. Radio telemetry showed that resting time was inversely correlated with time spent diving for fish during foraging trips (r=−0.95). Pigeon guillemots fed their chicks either Pacific sand lance Ammodytes hexapterus , a schooling midwater fish, which exhibited high interannual variance in abundance (CV=181%), or a variety of non-schooling demersal fishes, which were less variable in abundance (average CV=111%). Average resting times were 46% higher at colonies where schooling prey dominated the diet. Individuals at these colonies reduced resting times 32% during years of low food abundance, but did not reduce meal delivery rates. In contrast, individuals feeding on non-schooling fishes did not reduce resting times during low food years, but did reduce meal delivery rates by 27%. Interannual variance in resting times was greater for the schooling group than for the non-schooling group. We conclude from these differences that time allocation in pigeon guillemots is more flexible when variable schooling prey dominate diets. Resting times were also 27% lower for individuals feeding two-chick rather than one-chick broods. The combined effects of diet and brood size on adult time budgets may help to explain higher rates of brood reduction for pigeon guillemot chicks fed non-schooling fishes.     

The winter distribution of chinstrap penguins from two breeding sites in the South Shetland Islands of Antarctica

Satellite telemetry was used to determine the winter movements of eight chinstrap penguins from two breeding colonies in the South Shetland Islands, Antarctica during the 2000 and 2004 austral winters. Chinstrap penguins foraged largely inshore, on the shelf, north of the South Shetland Islands during 2000, but foraged mainly offshore in pelagic waters in 2004. Analyses of foraging trip durations during the chick-rearing periods that preceded the 2000 and 2004 winters suggest that prey were more abundant inshore during the summer of 2000 than in 2004. Oceanographic data further revealed the presence of a strong shelf-slope front in 2000 that was absent in 2004. In addition, two of the six chinstrap penguins from the colony in Admiralty Bay migrated from the South Shetland Islands region to the vicinity of the South Orkney and South Sandwich Islands, distances of 800 and 1,300 km, respectively. We postulate that the differences in winter migratory behavior among chinstrap penguins from this colony may reflect individual ties to different ancestral epicenters of chinstrap populations; one older and local in the South Shetland Islands and one relatively recent, arising from the emigration of chinstrap penguins that occurred during the expansion of this species in the mid-1900s.     

Nesting densities,productivity and survival of breeding Whimbrel Numenius phaeopus in Shetland

Between 1986 and 1988 data on the nesting densities, productivity, and survival of breeding Whimbrel Numenius phaeopus were collected from 5 study sites in the Northern Isles of Shetland. Nesting densities on sites varied between 11 and 21 pairs per 100 ha. Few studies elsewhere have recorded such high densities of nesting Whimbrel as those on certain sites used in the present study. Each breeding pair produced an average of between 0.75 and 0.91 fledglings per year. Productivity varied considerably between different study sites however, primarily because of differences in the survival rate of chicks between hatching and fledging (ranging from 3% to 55% in one year). The annual survival rate of breeding adults was at least 89%. Considering adult survival in relation to overall productivity, it appears likely that the production of fledglings from study sites is in excess of that required to balance adult mortality. This result is consistent with the current increase of the Whimbrel population in Shetland.     

The breeding biology of the starling Sturnus vulgaris in northern Finland

The breeding biology of the starling Sturnus vulgaris was studied in three populations in northern Finland, with additional reference localities in nearby areas. Results from a total of 329 nests are presented from years 1962-1976.
The onset of laying in the Oulu area took place on 5 May, the median date being 10 May, about one week later than in southern Finland and 2–3 weeks later than in central Europe. The clutch-size was 5.29 ± 0.05 in the first nests and 5.06 ± 0.26 in later ones. Incubation time was 12.1 ± 0.6 d. An average of 3.31 ± 0.10 fledglings was produced per pair, 3.69 ± 0.08 in succesful clutches, which is significantly less than usually reported from central Europe. Most of the losses were due to starvation of the young.
No second broods were observed in the Oulu area, and repeated nesting was not common, probably because of the general late start of laying.
The reasons for the recent decline in several Finnish starling populations do not lie in the production capacity but must be sought for elsewhere.     

The breeding biology of the Pacific Swallow Hirundo tahitica in Malaysia

The breeding biology of the Pacific Swallow was studied in Malaysia. Time-budgets and preliminary energy-budgets were calculated for different stages of the breeding cycle. Breeding was seasonal, the first eggs were laid in the first week of March from 1978 to 1982. The nest was a mud cup built under an overhang, often on man-made structures over water. The mean clutch size was 2.98 eggs. So more than two successful clutches were ever raised, although up to four sets of eggs can be laid if clutches are lost. The incubation period was 16.2 days and the nestling period 19–21 days. Nestling weights showed the typical hirundine recession before fledging. The mean brood size was 2.32 and there was no evidence of undernourishment in larger broods. Nesting success was lower than for temperate hirundines but high for a tropical passerine. Incubation duties were carried out by the female alone but both parents fed the brood. The male never delivered more than 44% of the total feeds. Daily energy expenditure varied from 3.44–4.9×BMR depending upon the stage of the breeding cycle.     

The effects of changes in food availability on the breeding ecology of great skuas Catharacta skua in Shetland

Great skuas on Foula, Shetland have responded to a decline in the availability of sandeels since the late 1970s by increasing the proportion of other items in their diets. This change is correlated with the annual recruitment of sandeels in Shetland waters. Since 1983 there has been a 10-fold increase in predation by great skuas upon other seabirds, as Furness & Hislop (1981) suggested might occur in response to a low availability of sandeels. Changes in diet have been accompanied by a 50% reduction in adult territorial attendance as adults increased their foraging effort, such that between 1987 and 1989 breeding adults were probably working as hard as they were able to. Despite this, breeding success was less than 40% in 1987 and less than 15% in 1988 and 1989. The major cause of breeding failure was predation of unguarded chicks by adults from neighbouring territories. The willingness of adults to expose their chicks to high predation risk is probably maintained because of a positive correlation between chick pre-fledging growth and post-fledging survival, which is expressed up to the age of two years and which will place a strong pressure upon adults to feed their chicks as well as possible. The high expenditure of effort by adults in 1987 and 1988 did not affect the weights of those birds incubating eggs in 1988 and 1989, but there was a slight (3%) decrease in egg size between the late 1970s and the late 1980s. Changes in the age structure of the breeding population and the absence in 1989 of 28% of adults colour-ringed during incubation in 1988 suggest an increase in the rate of egress since the 1970s. These changes probably represent an increase in the long-term costs of reproduction to adults at this colony.     

The breeding biology of the Namaqua Sandgrouse,Pterocles namaqua

The breeding biology of the Namaqua Sandgrouse, Pterocles namaqua, was studied and its nesting success determined through the observation of 278 nests over four consecutive breeding seasons at Droëgrond, Northern Cape Province, South Africa. The normal clutch of three eggs is laid over five days (±48-hour laying interval). The incomplete clutch is left unattended overnight, but is attended during the heat of the day by the female on days when an egg is laid and by the male on alternate days. After clutch completion, the pair share incubation, with the female relieving the male 151 min (±21 S.D.) after sunrise and the male relieving the female 105 min (±21 S.D.) before sunset. The incubation period is 21 days from clutch completion, and the three chicks normally hatch within 18 hours of one another. Nesting success ranged from 5.7% to 13.5% between seasons and averaged 8.2%. Predation, primarily by small mammals, was responsible for 96% of nest losses. Estimates of annual recruitment at Droëgrond ranged from minima of 3–10% to maxima of 6–20%, and are believed to be representative of a core area of the distribution of the Namaqua Sandgrouse in South Africa. These low estimates suggest that annual juvenile recruitment may be too low to maintain Namaqua Sandgrouse populations locally. Possible reasons for the sustained low level of breeding success are discussed.     

Age-related effects on breeding phenology and success of Common Guillemots Uria aalge at a North Sea colony

Capsule: Common Guillemots Uria aalge show delayed breeding and marked age-related changes in reproductive success consistent with improved performance with experience.

Aims: To determine age of first breeding and age-related effects on breeding phenology and success of Common Guillemots.

Methods: Resighting data from a long-term colour-ringing study of Common Guillemot chicks were combined with observations of breeding phenology and success to follow the recruitment process, breeding phenology and success of 62 birds at a major North Sea colony over a 30-year period.

Results: The median age of first breeding of Common Guillemots was 6.6 years. There were no detectable costs of first breeding on return rates or the likelihood of breeding the next season but first time breeders bred later and less successfully. Age of first breeding and lifetime breeding success both varied among individuals but there was no clear optimal age of first breeding and early first breeding was not associated with higher lifetime breeding success.

Conclusions: Common Guillemots in the Isle of May population delayed breeding for 3–4 years beyond physiological maturity. The marked increase in breeding success with age was consistent with improved performance with experience rather than selection for higher quality individuals. Findings from this study will inform population models by providing improved estimates of age of first breeding and age-related changes in reproductive performance.     

Vegetable biology and breeding in the genomics era

Vegetable crops provide a rich source of essential nutrients for humanity and represent critical economic values to global rural societies. However, genetic studies of vegetable crops have lagged behind major food crops, such as rice, wheat and maize, thereby limiting the application of molecular breeding. In the past decades, genome sequencing technologies have been increasingly applied in genetic studies and breeding of vegetables. In this review, we recapitulate recent progress on reference genome construction, population genomics and the exploitation of multi-omics datasets in vegetable crops. These advances have enabled an in-depth understanding of their domestication and evolution, and facilitated the genetic dissection of numerous agronomic traits, which jointly expedites the exploitation of state-of-the-art biotechnologies in vegetable breeding. We further provide perspectives of further directions for vegetable genomics and indicate how the ever-increasing omics data could accelerate genetic, biological studies and breeding in vegetable crops.

     

The breeding biology of lemon sharks at a tropical nursery lagoon

Surprisingly little is known about the reproductive behaviour and breeding biology of most shark species, especially in natural populations. Here, we characterize reproductive patterns and use of a natal nursery at Bimini, Bahamas by lemon sharks, Negaprion brevirostris. We systematically and exhaustively sampled young lemon sharks at Bimini annually from 1995 to 2000 and opportunistically sampled adults over the same period. Out of the 897 young sharks sampled, 119 could be assigned to five sampled mothers using microsatellite genotyping. Reproductive females showed strong philopatry to the nursery, returning to Bimini every two years to give birth. Each of these females may rely entirely on the Bimini nursery for recruitment. The protection of known nursery grounds should therefore figure prominently in conservation efforts for large coastal shark species. The reconstruction of paternal genotypes indicates that litters are sired by multiple males, and females mate with different males nearly every breeding cycle. The ubiquitous polyandry reported here raises the possibility that genetic incompatibility and post-copulatory paternity-biasing mechanisms may operate in viviparous sharks.