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Pesticides are implicated in the decline of insects

With almost one million described species, insects eclipse all other forms of animal life on Earth, not only in sheer numbers, diversity, and biomass, but also in their importance to functioning ecosystems. However, human-induced changes to the natural environment threaten vast numbers of these organisms and the vital services they provide to ecosystems. Leading causes of insect endangerment are habitat destruction or alteration of habitat by chemical pollutants (such as pesticides). Pesticides are implicated in the decline of many native bees and some aquatic insects.

Skylark, Corn Bunting, Tree Sparrow and Northern Lapwing in sharp decline across Europe

The Wild Bird Indicator 2005 shows that on average over the last twenty-five years, farmland birds such as the Eurasian Skylark Alauda arvensis, Corn Bunting Miliaria calandra, Eurasian Tree Sparrow Passer montanus and Northern Lapwing Vanellus vanellus, have declined sharply in number across Europe. As a whole from 1980 to 2003, common farmland birds on average fell in number by 28%.

Farmland birds showed a significant decline across Europe between 1990 and 2000

Between 1990 and 2000, farmland birds showed a significant decline across Europe, a trend not shared by bird assemblages of other habitats over the same period. Mean trends for each farmland species in the period 1990–2000 were positively correlated with trends over the period 1970–1990, and there was little change in population trajectory for most species over the 30-year period. Of the 58 species classed by an independent assessment as being primarily birds of farmland, 41 showed negative overall mean trends across Europe in 1990–2000. There was a significant negative correlation between mean national trends of all farmland species and indices of national agricultural intensity.

Alarming Insect-eating Bird Declines in Canada

An article by Bird Studies Canada biologist Jon McCracken examines substantial population declines for ‘aerial insectivores ‘ – birds that specialize on feeding on flying insects. The alarming trend, which appears to be most pronounced in Canada, has been revealed by the analysis of results from several bird monitoring programs, including the newly released Atlas of the Breeding Birds of Ontario, 2001-2005 and the North American Breeding Bird Survey.

Dramatic decline of an insectivorous passerine, the Whinchat

Insectivorous farmland passerines have declined steadily throughout most of western Europe over the past decades. The Whinchat Saxicola rubetra, an insectivorous passerine species of grassland, has undergone one of the most dramatic declines among farmland birds. The recent intensification of farming practices has led to a decrease in the availability of grassland invertebrates in general, and of important Whinchat chick-food in particular, even in remote Alpine valleys. This has a negative effect on reproductive success.

Songbirds on their way to extinction?

According to the latest update of "The Atlas of the Breeding Birds of Ontario" the list of songbird species in Ontario that are declining is staggering. "Population trends are generally positive for birds of prey, but biologists are expressing concern about the fate of grassland birds and those that feed on flying insects," says a statement from the organizers of the survey that led to the first update in 20 years.

Recent Declines of Sacramento’s Purple Martins Worries Biologists

Sacramento’s remnant population of the Purple Martin Progne subis, a swallow recognized as a state Species of Special Concern, declined again in 2008 according to a recent survey. The number of nesting martins declined to 84 nesting pairs, a 21% decline from last year. The population is at the lowest level recorded since surveys were initiated in the early 1990s. The continued population decline in Sacramento worries biologist Dan Airola, who has been studying and managing the purple martin population for years with a group of dedicated volunteers. “Over the last 4 years, the population has decreased by over 50%, which is pretty dramatic” Airola notes.

The explanation for farmland bird declines - Loss of insect food could be a major factor

Research into the declines of some species of farmland birds have shown that there is no single reason, but that different species have reacted to different factors, and that often, declines are associated with more than one factor impacting on a species simultaneously. Loss of insect food could be a major factor.

Comparative Losses of British Butterflies, Birds, and Plants and the Global Extinction Crisis

There is growing concern about increased population, regional, and global extinctions of species. A key question is whether extinction rates for one group of organisms are representative of other taxa. We present a comparison at the national scale of population and regional extinctions of birds, butterflies, and vascular plants from Britain in recent decades. Butterflies experienced the greatest net losses, disappearing on average from 13% of their previously occupied 10-kilometer squares. If insects elsewhere in the world are similarly sensitive, the known global extinction rates of vertebrate and plant species have an unrecorded parallel among the invertebrates, strengthening the hypothesis that the natural world is experiencing the sixth major extinction event in its history.