Birds of Sarcpa Lake, Melville Peninsula, Northwest Territories: Breeding Phenologies, Densities and Biogeography

Forty species of birds were observed during field studies at Sarcpa Lake, Melville Peninsula, N.W.T. during the summers of 1981 and 1982. Evidence of breeding was found for 22 species and the first definite breeding records for the Melville Peninsula were obtained for Glaucous Gull, Pectoral Sandpiper and Semipalmated Sandpiper and Semipalmated Sandpiper. A hybrid pair of gulls (Glaucous x Herring Gull) also nested and this appears to be the first definite North American record of such a hybrid nesting. Fourteen additional breeding species expected to be present, based on maps in Godfrey (1966), were not found. Average breeding bird density (35 pr/sq km) was comparable to that on Bylot Island, but considerably higher than that measured at other High Arctic sites. Neither average breeding bird densities nor phenologies changed appreciably from year to year despite a late spring melt in 1982. In both years birds began their breeding activities as soon as suitable nesting and feeding habitat became available. A biogeographic analysis based on the occurrence of breeding birds at 25 other sites across the Canadian Arctic indicates that the avifauna at Sarcpa Lake is more similar to those of High Arctic island sites than to those of mainland sites, but includes none of the species whose ranges are mainly within the Arctic Archipelago.Key words: arctic biogeography, birds, phenology, nesting density, Melville Peninsula, multivariate analysisMots clés: biogéographie arctique, oiseaux, phénologie, densité des nids, presqu'île Mclville, analyse à plusieurs variante

Consequences of pollinator availability and effectiveness for pollen transfer in a gynodioecious seed crop system

Pollinator availability and effectiveness are important considerations in plant systems that depend on insect transfer of pollen. In mixed-flower systems (such as dioecious or gynodioecious systems), pollinators may distinguish between morphs, a behaviour which could have negative implications if it leads to reduced cross-pollination. We examined pollinator visitation, response, and effectiveness in hybrid canola seed production, a gynodioecious crop, to understand how pollinator behaviour contributes to cross-pollination between 'male' (hermaphroditic) and 'female' (male-sterile) morphs. The pollinator types found in these fields differ in visitation rate, size, and pollen load, factors that may affect pollen transfer between plants. The willingness of pollinators to move between male and female flowers can also affect pollen deposition. We used an interview bouquet to present unvisited female inflorescences to different pollinator types visiting male and female flowers to understand behavioural responses to floral morphs and the factors that contribute to better pollination effectiveness. Managed pollinators (honey and leafcutter bees) were far more abundant than wild pollinators in this system. Bees foraging on male flowers were less likely to accept a proffered female flower than those foraging on female flowers. Pollen deposition on stigmas was influenced by pollinator type (female leafcutter bees were the most effective) and increased with time spent on a flower. Pollinators transferring from a male flower to a female flower deposited more pollen than those that originated on female flowers, emphasizing the importance of transfer between male and female morphs. Surprisingly, pollinators carrying more pollen transferred less pollen to recipient stigmas

Wing wear affects wing use and choice of floral density in foraging bumble bees

Damage to structures that enable mobility can potentially influence foraging behavior. Bumble bees vary in extent of individual wing wear, a trait predicted to affect mechanical performance during foraging. This study asks 1) do bumble bees distribute themselves across different floral densities in accordance with their concurrent wing wear? and 2) does wing use in foraging bumble bees depend on concurrent wing wear? We observed individually identifiable bumble bees foraging in 1-m 2 patches of high and low floral density of 3 plant types (Geranium viscosissimum, Melilotus alba/officinalis, and Monarda fistulosa). Bee preference for flower density was determined by an interaction between wing area and bee body size: small worn-winged bees selected patches of higher density, whereas large worn-winged bees selected patches of lower density. Bees with more worn wings spent less time in flight and flew less often; however, only foragers collecting pollen appeared to reduce wing-use behavior (i.e., wing collision frequency) that leads to loss of wing area. This study demonstrates that individuals respond to wing damage in different ways depending on their body size and foraging task. Wing wear clearly influences foraging behavior of worker bumble bee

Shape of wing wear fails to affect load lifting in bumble bees with experimental wing wear

Wing wear reflects the accumulation of irreversible damage to an insect’s wings over its lifetime, and this damage should influence flight performance. In the case of bumble bees, flight seems robust to variation in wing area asymmetry and air pressure, but not to loss of wing area. However, how the pattern of wing wear affects flight performance remains unstudied. In nature, wing wear typically occurs in a ragged and haphazard pattern along the wing’s trailing margin, a shape strikingly different from the straight cut applied in past studies. In this study, we test if shape of wing wear (implemented as 4 distinct treatments plus a control) affects maximum load lifting capabilities and wingbeat frequency of worker bumble bees (Bombus impatiens Cresson 1863). We found that shape of wing wear of 171 mg bees had no detectable effect on maximum load lifting capability (detectable effect size = 18 mg) or on wingbeat frequency (detectable effect size = 15 Hz), but that loss of wing area reduced load lifting capability and increased wingbeat frequency. The importance of wing area in explaining the load lifting ability of bumble bees is reinforced in this study. But, paradoxically, shape of wing wear did not detectably affect lift generation, which is determined by unsteady aerodynamic forces in these lift-reliant insects.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author