English

We examined the possibility that granular insecticides, used intensively in the Canadian prairies to control flea beetles (Phyllotreta sp.) in canola (Brassica napus and B. napa), could contribute to bird population declines.

A retrospective analysis (1971–96) was done to investigate relationships between counts of 29 bird species made on Breeding Bird Survey (BBS) routes with a spatially explicit granular use index (derived from surveys made in 1980–85) and an index of land use change (derived from Principal Components Analysis of agricultural statistics) for 30 Census Agricultural Regions (CARs). Controlling for spatial location and the land use change index, abundance of American robin (Turdus migratorius), horned lark (Eremophila alpestris), house sparrow (Passer domesticus), mourning dove (Zenaida macroura), and western meadowlark (Sturnella neglecta) was negatively correlated with insecticide use; only two species showed evidence of a positive correlation. At a shorter time scale, for which we had direct estimates of pesticide use (1980–85), we also found evidence that the black-billed magpie (Pica pica), European starling (Sturnus vulgaris), and killdeer (Charadrius vociferus) were less abundant in areas where granular insecticide use was high. Population trends (% annual change between 1971–96) were negatively correlated with the granular index for horned lark, house sparrow, and western meadowlark. Although correlational only, our results suggest that granular insecticides may be an important factor influencing population changes in some bird species in prairie farmland.

In the Netherlands, 766 species of larger moths are considered native. About one-third of the species are decreasing and all species together show a significant, declining, trend in abundance. It may well be that the severe decline in some bird species in Northwestern Europe, especially of those that inhabit agricultural landscapes like Corn Bunting (Miliaria calandra) and Eurasian Skylark (Alauda arvensis), is related to the decline in moth diversity. It can be hypothesized, that the most important trigger is the period in which these birds feed their young.

We studied arthropod occurrence in fallow land, extensively used pastures, extensively used meadows (cut twice or three times a year) and intensively used meadows (cut more than three times ayear) in Upper Bavaria.

Medium-sized arthropods (5-15mm) were encountered much less frequently on intensively used and fallow land than on pastures and extensively used meadows. Large individuals (>15mm) were observed most frequently on pastures but were hardly found on intensively used meadows. In autumn they occurred almost exclusively on pastures and fallow land. Species richness was the highest on pastures and the lowest on intensively used meadows. The study underscores the depletion of arthropod fauna and in particular the decline of large arthropods on intensively used meadows. It indicates that extensively used meadows and extensively used pastures in particular are the most favourable sources of nutrition for insectivores such as reptiles, amphibians, birds or bats.

Aerially-foraging insectivorous birds have experienced dramatic population declines in North America over the past several decades, but a dearth of data on their limiting factors makes hypotheses about these declines difficult to test. The common link among these declining species is their diet and it is therefore likely that avian population changes are linked to changes in insect prey. We determined that the onset of the population crash for chimney swifts was associated with 1) a major reduction in the amount of beetle and bug prey, and 2) an increased reliance on fly prey. The causes for these changes in prey base remain to be seen, but may be related to historical use of pesticides and contaminants. If chimney swifts serve as a model species for all aerially-foraging insectivores, then our study may have revealed the historical proximate mechanism for their guild-wide decline.

The Chimney Swift Chaetura pelagica is a little, high-flying, dark grey bird whose diet consists entirely of insects caught on the wing. It spends summers in eastern North America and winters in South America. In the 40 years since 1968, Chimney Swift numbers in Canada have declined by 96% (8.3% annually, on average).

Widespread and familiar, the Barn Swallow (Hirundo rustica) is well monitored in Canada by the Breeding Bird Survey (BBS). BBS data show a relatively stable population from the 1970s to the late 1980s followed by a steep, persistent decline through the late 2000s.

North American birds that feed on aerial insects are experiencing widespread population declines. An analysis of the North American Breeding Bird Survey trend estimates for 1966 to 2006 suggests that declines in this guild are significantly stronger than in passerines in general.

Of the world’s threatened birds (n = 1,253 Critically Endangered, Endangered and Vulnerable bird species. Analysis of data held in BirdLife’s World Bird Database, 2011), over 80% have populations that are currently in decline, just 9% are stable, whilst only 5% are increasing (largely owing to conservation action). For 3%, the direction of the current trend is unknown or unset.