Nodding thistle receptacle weevil Rhinocyllus conicus and gallfly Urophora solstitialis attack the capitula of nodding thistle Carduus nutans L Between 31 October and 15 December 2003 the phenology of both R conicus and U solstitialis was studied at a dryland site in Canterbury Adult R conicus were more numerous than U solstitialis on capitula throughout the experiment Larvae of R conicus were first found on 11 November (15 of capitula infested) and peaked on 2 December with 53 of capitula infested Only 3 of capitula were infested by U solstitialis Adult R conicus or U solstitialis emerged from 79 of the selected primary and secondary capitula The majority of infested capitula (81) contained only R conicus 2 contained only U solstitialis while 17 contained both insect species Parasitism of R conicus by the braconid parasitoid Microctonus aethiopoides was low and occurred when most weevil eggs had been laid
AbstractSympatric species must sufficiently differentiate aspects of their ecological niche to alleviate complete interspecific competition and stably coexist within the same area. Seabirds provide a unique opportunity to understand patterns of niche segregation among coexisting species because they form large multi-species colonies of breeding aggregations with seemingly overlapping diets and foraging areas. Recent biologging tools have revealed that colonial seabirds can differentiate components of their foraging strategies. Specifically, small, diving birds with high wing-loading may have small foraging radii compared with larger or non-diving birds. In the Gulf of St-Lawrence in Canada, we investigated whether and how niche differentiation occurs in four incubating seabird species breeding sympatrically using GPS-tracking and direct field observations of prey items carried by adults to chicks: the Atlantic puffin (Fratercula arctica), razorbill (Alca torda), common murre (Uria aalge), and black-legged kittiwake (Rissa tridactyla). Although there was overlap at foraging hotspots, all species differentiated in either diet (prey species, size and number) or foraging range. Whereas puffins and razorbills consumed multiple smaller prey items that were readily available closer to the colony, murres selected larger more diverse prey that were accessible due to their deeper diving capability. Kittiwakes compensated for their surface foraging by having a large foraging range, including foraging largely at a specific distant hotspot. These foraging habitat specialisations may alleviate high interspecific competition allowing for their coexistence, providing insight on multispecies colonial living.