Colony Occupation Research Articles

Human presence outweighs non-anthropogenic factors as a driver of avian nest parasite loads

Human presence and landscape change can alter many aspects of ecological communities and can interact with natural factors to change host–parasite dynamics. In the study reported here, we tested whether an anthropogenic factor, urbanization, affected the abundance and size of hematophagous ectoparasites (swallow bugs: Oeciacus vicarius) found in the nests of cliff swallows (Petrochelidon pyrrhonota). We also examined how swallow bug infestations might be affected by multiple non-anthropogenic biotic and abiotic factors, including season, nest mass, nest colony size, the history of colony occupation, and the presence of other parasitic and non-parasitic arthropods in cliff swallow nests. Our sample included 73 nests collected from 18 cliff swallow colonies in Northern Colorado, USA. Results indicated that swallow bug loads were most strongly predicted by human land use and density, with urban colonies having much heavier infestations than rural colonies. Swallow bugs were more numerous in colonies that were known to have been recently occupied by cliff swallows, and in nests that contained high numbers of other parasitic arthropods, including fleas and ticks. Swallow bug population size did not vary with season, nest mass, or nest colony size, and none of our measured factors predicted swallow bug body length. Results suggest that cities may exacerbate harmful effects of avian ectoparasites by promoting large population sizes, and that these effects may be compounded by the presence of multiple parasitic species in heavily infested nests.

The importance of protected and unprotected areas for colony occupancy and colony size in White-necked Picathartes Picathartes gymnocephalus in and around Gola Rainforest National Park, Sierra Leone

SummaryMost attention on tropical biodiversity conservation has focussed on protected areas. Recognising and enhancing the value of biodiversity outside, as well as inside, protected areas is increasingly important given recognition that biodiversity targets will not be met through protected areas alone. We investigated the extent to which protection influences colony occupancy and colony size of a species of conservation concern, the rock-nesting White-necked Picathartes Picathartes gymnocephalus. We used mixed models to compare long term trends at 42 colonies located both inside and outside a protected area of forest, Gola Rainforest National Park, and considered colonies further inside the boundary as being better protected. Colony occupation was primarily predicted by the level of protection, with occupation highest within protected areas, but was not different between colonies situated close to or far from the boundary. Mean colony occupation was consistently high in protected areas, and lower in unprotected areas. The surface area of colony rocks was also an important predictor with larger rock faces having a higher probability of occupancy. Our best models also included distance to forested habitat, presence of cleared forest and evidence of hunting as less important predictors. Over the eight-year study, after controlling for rock surface area, active colony size declined significantly. However, declines were only significant in colonies in unprotected forest, whilst colonies located within protected areas were buffered from significant decline. Together this suggests colony occupancy and the number of active nests are influenced by protection and human disturbance. Although a lack of demographic and population dynamic work on picathartes prevents identifying mechanisms, we show that despite unprotected colonies having lower occupancy and fewer active nests they can persist in human altered and disturbed areas, partly because larger traditionally used rocks remain important nesting sites.

Population increase and nest-site selection of Cattle Egrets Bubulcus ibis at a new colony in drylands of north-east Algeria

Colony occupation by Cattle Egrets Bubulcus ibis at an arid location in north-east Algeria lasted from mid-March or April to August. The colony, which was founded in 2003, increased from 124 pairs in 2007 to 250 pairs in 2011 and the density of nests from 0.36 to 0.73 nests m−2 in the same period. The number of trees used for nesting increased from 16 trees in 2007 to 40 in 2011. The average height of nesting trees ranged from 12.8 士 3.0 m in 2007 to 13.6 土 2.9 m in 2011, whereas the average height of nests varied between 11.5 土 2.5 m and 13.2 土 2.9 m. Cattle Egrets built their nests mainly on strong primary branches of trees (30%) or secondary branches at the periphery of the tree's crown (29%). Numbers of nests sited in a tree were significantly influenced by the species of tree and the diameters of its trunk and crown, as well as by the horizontal and vertical positions of nests within the tree.

Ross’s Gull (<i>Rhodostethia rosea</i>) Breeding in Penny Strait, Nunavut, Canada

We found a small, previously undiscovered breeding colony of Ross’s gulls (Rhodostethia rosea) in Nunavut, Canada, approximately 80 km from a previous colony location occupied during the 1970s. The birds nested in association with arctic terns (Sterna paradisaea). The collective observations from this region of the High Arctic suggest that Ross’s gulls may move colonies each year, or that colony occupation is intermittent.

Declines in abundance and distribution of the ivory gull (Pagophila eburnea) in Arctic Canada

The ivory gull (Pagophila eburnea) is a seabird that inhabits Arctic oceans throughout the year, often in association with polar pack ice. It is rare (<14,000 breeding pairs globally) and remains one of the most poorly known seabird species in the world. Canada supports breeding populations of international significance, and residents of communities in the Canadian High Arctic currently observe fewer ivory gulls than they did in the 1980s. However, no population trend data existed for this species in Canada prior to this study. We initiated aerial surveys in July 2002 and 2003 of most known ivory gull colonies in Canada to assess current population levels. Forty two colonies were visited, 14 of which were new discoveries. We recorded an 80% decline in numbers of nesting ivory gulls. Several of the largest known colonies were completely extirpated and those that remained supported significantly fewer nesting birds than previously observed. Results were similar in both years despite some differences in local sea ice conditions, suggesting a numerical decline in the population and not simply annual fluctuations in colony occupation. Declines have occurred in all habitat types and across the known Canadian breeding range, suggesting that causes of the decline may be related to factors occurring during migration or on wintering grounds. We recommend that international efforts now be directed at assessing population status and trends of this species in other circumpolar countries.

Maximum possible age of a petrel breeding colony near Punakaiki (South Island, New Zealand) from radiocarbon and stable isotope analysis of soil

The lifetime of individual petrel colonies is poorly known. This study used radiocarbon, 13C, and 15N analysis of soil to determine the maximum possible age of a colony presently occupied by Westland petrels. A sample of Ap horizon soil in lithic contact was selected for analysis, as soil least likely to have been redistributed by petrel burrowing. Chemical removal of mobile organic matter decreased δ15N from 14.0‰ (typical of breeding colony soils) to 6.1‰ (within the range of temperate forest soils without sea‐bird breeding). δ13C values changed little, from ‐27.1‰ (untreated soil) to ‐28.4‰ (treated soil), and were typical of forest soil with C3 vegetation and no incorporation of marine C. Duplicate AMS radiocarbon analysis of treated sample yielded a combined conventional radiocarbon age of 864 ± 32 BP, indicating that sea‐bird breeding could not have occurred at the site for more than 740–960 calendar years. Initial colony occupation may have occurred much later than this, and not been continuous. Sea bird species other than Westland petrels may also have used the site.

Abandoned penguin colonies and environmental change in the Palmer Station area, Anvers Island, Antarctic Peninsula

Six abandoned colonies of Adélie penguin (Pygoscelis adeliae) were excavated near Palmer Station, Anvers Island, Antarctic Peninsula, to investigate the occupation history of this species. Sediments from each site yielded abundant fish bones and otoliths and squid beaks that represent prey remains deposited by penguins during the nesting period. Radiocarbon analyses indicate that colony occupation began prior to the Little Ice Age (LIA; 1500–1850 AD), with the oldest site dating to 644 yrs before present (BP; average reservoir-corrected date with Is range, 603–679 yr BP). Food remains indicate that the non-euphausiid prey of penguins consisted primarily of a mesopelagic squid (Psychroteuthis glacialis) and two species of fish (Pleuragramma antarcticun and Electrona antarctica). The relative abundance of the first two prey taxa varied significantly among six sites (X2&gt;34.6; df = 10; P &lt;0.001) with colonies dating prior to the LIA having greater representation of squid, and less of silverfish, than those occupied during the LIA. Data from control excavations at three modern colonies indicate a diet similar to that of the pre-LIA sites. These results suggest that Adélie penguins may have changed their diet in response to warming and cooling cycles in the past. In addition, only Adélie penguins are known to have nested in the Palmer Station area prior to the l950s; gentoo (Pygoscelis papua) and chinstrap (P. antarctica) penguins now breeding in this region have expanded their ranges southward in the Peninsula within the past 50 yrs, in correlation with pronounced regional warming.

Parental Investment by the Sexes in the Herring Gull: The Use of Energy Reserves during Early Breeding

A sample of culled birds was used to determine weight change and size of endogenous nutrient reserves in male and female Herring Gulls Larus argentatus during the period from colony occupation to late incubation. Both sexes showed considerable variation in body condition according to breeding phase. The most striking difference between the sexes was found in lipid contents prior to laying. Whereas males tended to deplete endogenous fat, females gained fat. There was no marked change in protein reserves in either sex. It is concluded that males meet maintenance costs during courtship feeding by using a great deal of their endogenous fat while saving the proteins. This is done in favour of the body condition of the laying female, males thus equalizing the initial parental investment of the two sexes. Both sexes regained energy reserves during incubation, being in equal physiological condition when the

Factors Influencing Colony Attendance by Pigeon Guillemots on Southeast Farallon Island, California

I studied colony attendance in a marked sample of Pigeon Guillemots (Cepphus columba) in 1979 and 1980 on Southeast Farallon Island, California. These observations were supplemented with sightings of known-age birds in 1977, 1981, and 1982. In 1979 and 1980 I compared the attendance of males and females from the time of colony occupation through the incubation and chick-rearing periods. Guillemots returned in early March in both years, but occupied territories earlier in 1979 than in 1980. Older, experienced birds arrived on land before young, nonbreeders. Males arrived earlier than females each year and spent more time on their territory each morning before and after egg laying. In 1979, colony attendance was higher for both sexes, egg laying began earlier, larger clutches were laid, and young chicks were fed at a higher rate. I suggest that the annual differences in attendance and egg laying dates may have been due to the greater availability of food in 1979, as measured by higher chick-feeding rates. Sex differences in attendance probably result from the increased energetic requirements associated with egg formation in females.

Studies on a colony of colour-ringed Herring GullsLarus argentatus: II. Colony occupation and feeding outside the breeding season

The study of colour-ringed Herring Gulls over 6 years at a colony in NE England has shown that many of the breeding birds are present in every month of the year. A majority of the adult females leave the colony for a month or more during the non-breeding season but this absence is not sychronized and some of the birds have returned before others depart. Only a minority of the adult males leave the colony for periods in excess of a month and they appear to be more attached to the colony throughout the year than the females. Most of the birds remain within 25 km of the colony during the annual absence from the colony. Young breeding adult Herring Gulls may leave the colony for longer periods. Very few of the birds were found feeding at fish quays or refuse tips in the area and even those which did visit these feeding sites, did so infrequently. It is suggested that most of the birds feed at sea.

Colony behavior of the obligate social parasiteVespula austriaca (Panzer) (Hymenoptera: Vespidae)

The obligate social parasite,Vespula austriaca (Panzer), after successfully usurping a colony, displayed overt physical dominance of the host workers,V. acadica (Sladen). Agonistic inquiline behavior such as mauling, chasing workers, and flailing were commonly observed during observations of 5 parasitized colonies. The parasites solicited workers more frequently than larvae for liquid nourishment, and commonly engaged in both typical and forced trophallaxis. Aggressiveness of the parasite was more intense during the early stages of colony occupation, and was less frequent and vigorous in the later stages of the colony. A brief, and probably intense, oviposition period occurred during the period of heightened parasite aggression. This species exhibited many activities similar to those of another vespine inquiline,Dolichovespula arctica (Rohwer), such as hyperactivity, gastral dragging, minimal nest construction and lack of colony defense, but also displayed some contrasting interactions. There was an absence of worker attraction to the inquiline, an inhibition of worker ovarian development by the parasite, and decreased aggression in later colony stages. It is hypothesized thatV. austriaca maintains colony control through an interplay of direct and forceful interactions with workers and by the use of pheromones.

THE PROCESS OF COLONY FORMATION AMONG HERRING GULLS LARUS ARGENTATUS NESTING IN NEW JERSEY

SummaryWe examined the pattern of colony occupation and egg‐laying in five colonies of Herring Gulls nesting in New Jersey, U.S.A. Colonies formed from epicentres located in sparse bushes. The number of epicentres related to the number of birds nesting in the colonies. Colonies of over 250 pairs had more than one epicentre, whereas those with under 250 pairs had only one epicentre. Epicentres were not always in the geographical centre of the colonies. New territory‐hunting pairs filled in the epicentre areas, and then nested outside these areas. The egg‐laying pattern followed the settling pattern, but was more synchronous than the settling pattern. There was greater synchrony of egg‐laying within sub‐areas of the colonies than in the colonies as a whole. Further, synchrony correlated with the number of nests in sub‐areas.