Zwaluwen

The decline of aerial insectivores could be related to large-scale insecticide use since the mid 1900s

The current population size for Common Nighthawks Chordeiles minor in Canada is estimated at 400,000 breeding adults. In Canada, data from the Breeding Bird Survey (BBS), indicate a significant long-term (i.e. 1968-2005) decline of 4.2% per year. In the most recent 10 year period (1995-2005), BBS data show a significant decline of 6.6% per year. This corresponds to a 49.5% decrease in the population. While there are no specific studies on the subject, the decline of the Common Nighthawk may be partly related to a general decline in insect populations in both the breeding and wintering grounds, due to large-scale insecticide use since the mid 1900s.

Massive Common Nighthawk Decline in Canada

In April of 2007, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) recommended that the Common Nighthawk Chordeiles minor be included on Schedule 1 of the Species at Risk Act. Areas surveyed over the last three generations have shown an almost 50 percent decline in the species! Reasons for its decline may include reductions in the number of insects and loss of the open habitat in which it thrives.

The proverbial clock may well be ticking down on many common species of aerial insectivores in Canada

The guild of ‘aerial insectivores’ – birds that specialize on feeding on flying insects – includes Whip-poor-wills Caprimulgus vociferus, nighthawks, swifts, swallows, martins, and flycatchers. Early results from the second Ontario Breeding Bird Atlas indicated some startling declines and even range contractions for this guild. The magnitude of the declines, especially within the past 20 years or so, is alarming.

Most of the avian insectivores are declining in northeastern North America

For decades now, Ontario’s skies have been losing not only whip-poor-wills Caprimulgus vociferus but many of their fellow aerial insectivores – that agile “guild,” or group, of birds that feasts on the wing, snapping up airborne insects. “Frankly, most of the avian insectivores are declining in northeastern North America,” says Mike Cadman, a songbird biologist with Canadian Wildlife Service (CWS), Ontario region, in Burlington. He quickly reels off a list of species: “Swallows, nightjars, a lot of the flycatchers and the swifts … We have no clue why that would be, and it seems fairly consistent across the group.”

The Whip-poor-will has joined the ranks of bird species facing declines in Canada

For the first time ever in Canada, the Whip-poor-will Caprimulgus vociferus has joined the ranks of bird species facing declines in their populations. At their annual meeting in April, 2009 the Committee on the Status of Endangered Wildlife in Canada, or COSEWIC, recommended that the Whippoorwill be added to Canada's list of species at risk. Their recommendation is based on a 10% decline over the past decade for the species due to declining habitat and fluctuating insect populations.

De nachtzwaluw weet zich te handhaven binnen de resterende kerngebieden op de Veluwe en Noord-Brabant

Rond het begin van de 20e eeuw broedden enkele duizenden paren nachtzwaluwen Caprimulgus europaeus in ons land, met name op de oostelijke en zuidelijke zandgronden en in de duinstreek. Vanaf 1940 of 1950 was sprake van een duidelijke afname. De aantallen van de nachtzwaluw werden rond 1960 geschat op 1.500-2.000 paren. Rond 1975 waren minder dan duizend paren over en was het westen des lands vrijwel ontvolkt. Sindsdien zijn de laatste bolwerken in het noordoosten - op het Bargerveen na - ook vrijwel verlaten. Begin 90'er jaren broedden er nog 450 tot 600 paar nachtzwaluwen in ons land. Volgens SOVON is er sinds het midden van de jaren '90 sprake van een herstel van de nachtzwaluwpopulatie, grotendeels binnen de resterende kerngebieden: zowel op de Veluwe als in Noord-Brabant namen de aantallen weer toe.

Rückgang der Uferschwalbe in Brandenburg von fast 65 Prozent seit 1995

Uferschwalben Riparia riparia zählt die Rote Liste Brandenburgs mittlerweile zu den stark gefährdeten Vogelarten. Konnten 1995 noch 15 000 bis 20 000 Brutpaare erfasst werden, gingen EU-Naturschutz-Experten rund zehn Jahre später davon aus, dass nur noch 5000 bis 7000 Pärchen in Brandenburg brüten. Ein Rückgang von fast 65 Prozent.

De oeverzwaluw handhaaft zich in Nederland maar gaat in Vlaanderen en Luxemburg achteruit

De oeverzwaluw Riparia riparia broedt in zelfgegraven holen in zandige rivieroevers en verder overal waar verticale zandwanden aanwezig zijn. Kerngebieden van de oeverzwaluw bevinden zich in het rivierengebied inclusief het zuidelijke Maasdal. De oeverzwaluw broedt verder in Zuidelijk Flevoland, de omgeving van de Randmeren, Oost-Groningen, Oost-Friesland en Lauwersmeer en westelijk Noord-Brabant/Oost-Zeeland. Vliegende insecten vormen het voedsel en worden in de wijde omgeving van de broedplaats bejaagd. De eerste degelijke schatting van het aantal broedende oeverzwaluwen stamt uit midden jaren zestig; zo'n 25.000 paar. Midden jaren zeventig was het broedbestand geslonken tot 5000-8000 paar, een afname die zich doorzette tot 1985, toen met 3500 paren een dieptepunt bereikt werd.

Drastische Rückgänge bei Insekten fressenden Vögeln

Kanadische Wissenschaftler schlagen Alarm: In den letzten 20 Jahren haben die Bestände von häufigen Insekten fressenden Vogelarten in Kanada um bis zu 70% abgenommen. Die kanadischen Forscher haben insbesondere Rückgänge bei der auch in Europa vorkommenden Uferschwalbe Riparia riparia und dem Schornsteinsegler Chaetura pelagica, einem engen Verwandten unseres Mauerseglers Apus apus, festgestellt.

Historical declines in chimney swift populations are associated with dramatic changes in insect prey consumption

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.