Swallows

Long-term Population Decline is Decimating Aerial Insectivores

Concerned with the dramatic decline of 17 species of birds that nest in Connecticut and eat only insects caught while flying, Connecticut Audubon Society today called for a multi-agency program of research and assessment along with immediate remedies such as cuts in pesticide use and the creation of man-made nesting sites. The recommendations and action plan are contained in the Connecticut State of the Birds 2013 report, “The Seventh Habitat and the Decline of Our Aerial Insectivores.” Released annually since 2006 by Connecticut Audubon Society, Connecticut State of the Birds has become the leading research-based assessment of conservation conditions in the state. The 17 species – known as aerial insectivores because they eat bugs on the wing – include beautiful and well-known birds such as Barn Swallows, Whip-poor-wills, Common Nighthawks, Chimney Swifts, Purple Martins and Tree Swallows. They are suffering from a long-term population decline that, if unchecked, threatens their survival. The report also contains an article about a similar decline in Connecticut’s bat population, which is also entirely reliant on aerial insects.

Maar liefst 38% minder Boerenzwaluwen in Woudsend e.o. in 2012 dan in het jaar daarvoor

We vernamen al berichten dat het met de Boerenzwaluw (Hirundo rustica) niet goed gaat. Maar dat de gevolgen voor de telling rond Woudsend zo dramatisch zouden zijn hadden we niet gedacht. Vorig jaar werden 228 bewoonde nesten geteld maar dit jaar kwamen we (ook weer rond 13-15 juni) niet verder dan 141; een achteruitgang van 38% ! Het aantal adressen waar genesteld wordt nam af van 38 naar 36. Op 24 adressen was het aantal (aanzienlijk) lager, op 6 adressen was het aantal hoger en op 6 adressen bleef het gelijk.

De oeverzwaluw heeft in Vlaanderen zware klappen gekregen

Het gaat niet goed met onze zwaluwen. Recente tellingen van de aantallen wijzen uit dat alle zwaluwsoorten met 50 % tot 80 % achteruit gegaan zijn. In Vlaanderen zijn de belangrijkste oorzaken de daling van het aantal insecten door gebruik van insecticiden en de achteruitgang van het broed- en leefgebied. Van onze drie inheemse zwaluwsoorten is de oeverzwaluw (Riparia riparia) wellicht de minst bekende soort. Hij broedt, in tegenstelling tot z’n bekende neven de Boerenzwaluw (Hirundo rustica) en Huiszwaluw (Delichon urbicum), niet in schuren, stallen of onder dakgoten, maar wel in zandige oevers, afgravingen en zanddepots. Het aantal broedparen in Vlaanderen wordt momenteel op 5.000 geraamd. Een daling van maar liefst 70 % ten opzichte van 1968 (ca. 15.400 broedparen).

Swift decline of 40% in Britain in the past decade

The swifts are going now from our village. Perhaps we should pause to enjoy them one last time before the final few depart. The miracle of swifts, perhaps the miracle of all life, is made more apparent if you think of them not as birds, but as insects. For swifts are made from nothing but tiny invertebrates floating in the ether. A flock of 30 and everything about them — that noise, those scintillating movements, their feathers, those air-filled bones as light as grass — is a distillation of billions of insects. And when I say billions, I mean it. A single mouthful of food passed from an adult swift to its chick can contain 300 insects. Alas, the miracle of swifts is fading. In the past decade they've declined in Britain by 40%. Just as we might see the swifts' sky-trawl as composed of nothing but insects, we should recall that our own dance consumes almost every other living thing around us.

The staggering decline of aerial insectivores is a dire warning for the health of nature across the Americas

Barn swallows are birds with a long history of associating with people. They frequently make their mud nests under the eaves of houses, stables and barns. These summer visitors fly enormous distances from South America to raise chicks in Canada, then gather in chattering flocks on overhead wires before heading south again for the winter. Shockingly, this once common and familiar bird has suffered drastic declines in population in recent decades. Since 1970, they have declined to less than a quarter of their previous number. The dramatic loss of these once common, artistically swooping, aerial insect-eaters, that brighten our countryside, is almost inexplicable. It should be a dire warning for the health of nature across the Americas.

New Hampshire's ‘State of the Birds' - “Empty Skies: The Decline of Aerial Insectivores”

For some strange reason, since the old beaver families ran out of the food they enjoyed and moved on, our skies have appeared less occupied with winged insect eaters. Before that we saw every single species of swallows, except the purple martin Progne subis. These included the barn Hirundo Rustica, which nested in our old buildings, the tree Tachycineta bicolor, that used our birdhouses to raise their young, and the cliff Petrochelidon pyrrhonota, who built their jug-like nests under our barn eves. The rough-winged Stelgidopteryx serripennis and bank swallows Riparia riparia flew up from the Ashuelot River and over our pond to fill up on insects. The large flocks of swallows were accompanied by chimney swifts (Chaetura pelagica) that nested each summer in one of the flues in our house chimney. (While eating our meals in the kitchen, we could hear them chatter.) There were other insect eaters, too, that appeared for a good feed at the pond. Larger flycatchers such as: Phoebe (Sayornis phoebe), kingbird (Tyrannus tyrannus), eastern pewee (Contopus virens), and olive-sided (Contopus cooperi), as well as each of the five species of Empidonax flycatchers. These quite small species are somewhat difficult to separate one from the other, unless one hears them “speak.” Their voices can be differentiated, one from the other. In late years, all of these species, including whip-poorwills (Caprimulgus vociferus), (goatsuckers) have, or nearly have, disappeared from our fields, woods, and dooryard. The change happened gradually, from one year to another, but by now, has become definitely noticeable. Truth to tell, I should not have been surprised to read the cover story in NH Audubon's Spring Issue, 2012, of “Afield” headlined: “Empty Skies: The Decline of Aerial Insectivores,” written by Dr. Pamela Hunt, bird conservation biologist of the organization. My surprise came from seeing in black and white, what had become selfevident in the past few years here at the farm.

Der Einsatz von Pestiziden ist zu einer ernsthaften Bedrohung für viele Seglerarten geworden

Mauersegler (Apus apus) verbringen fast ihr ganzes Leben in der Luft. Neben der Nahrungssuche und dem Trinken meistert er auch das Schlafen, die Gefiederpflege und die Paarung im Flug. Lediglich zur Brut und Jungenaufzucht wird "Bodenkontakt" aufgenommen. Mauersegler fressen nur in der Luft schwebende Insekten und Spinnen. Nur wenige Vögel stehen in so ambivalenten Beziehungen zum Menschen wie die Segler. Mauersegler sind mittlerweile zu 99 Prozent Bewohner menschlicher Siedlungen. Durch Altbausanierungen und die hermetische Abriegelung der Neubauten werden Nistmöglichkeiten für den Koloniebrüter immer knapper. Auch der Einsatz von Insektiziden und Herbiziden ist zu einer ernsthaften Bedrohung für viele Seglerarten geworden. Eine natürliche Gartengestaltung und der Verzicht auf Insektizide kommen dem Mauersegler und zahlreichen anderen Gartenvögeln zugute. An den heimischen Sträuchern und Blumen finden sich viele Insekten, die nicht nur dem Mauersegler als Nahrung dienen. Es ist zu befürchten, dass diese jetzt noch häufigen Vögel, die über Jahrhunderte mit ihren Flugspielen und Rufen die Sommerabende unserer Städte belebten, aus dem Siedlungsbild ebenso unaufhaltsam verschwinden werden, wie sie es einstmals für sich erobert haben.

There's an alarming decline in chimney swifts in North America

There's an alarming decline in chimney swifts (Chaetura pelagica), the so-called "flying cigars" that on summer nights eat about one-third their weight in insects. Numbers of the elusive birds are dropping in Connecticut by about 4 percent annually, experts say, with the possibility they could all but disappear from the state in a few decades unless the trend is reversed. Other states are reporting dramatic declines, too. In Minnesota, for example, the bird's numbers have dropped about 48 percent in the last four years, according to the Minnesota Audubon Society. And Canadian biologists are reporting a "dramatic" decline in numbers, too, with populations there sinking 30 percent in the last 15 years. Experts note that many other North American insectivore bird species, such as nighthawks Chordeiles minor and whip-poor-wills Caprimulgus vociferus, are also in dramatic decline, which would also point to a lack of food as a possible cause for their difficulties.

Late-arriving barn swallows linked to population declines

Barn swallows (Hirundo rustica) are arriving later in the spring than they did 30–40 years ago at numerous sites in Korea. In some cases their arrival times are later by more than 1 month. This result is perplexing as spring activities of plants and animals are generally getting earlier due to warming temperatures. The first arrival dates of swallows are not related to temperature, suggesting that another factor is involved. On the basis of a questionnaire, a large majority of long-term observers are confident that there has been a moderate to severe decline in swallow populations at their field site over the study period. The greatest delays in arrival times are associated with sites with more severe reported declines in population size. Simulations using trapping data of large migratory bird populations from the United States, consisting of hundreds of individuals, suggest that severe population declines of 99% can result in delays of 10–12 days in arrival times.

Der Pestizideinsatz in der Landwirtschaft zerstört die Nahrungsgrundlage der Schwalben

Die Mehlschwalbe (Delichon urbicum) gehört zur Familie der Schwalben (Hirundinidae), zu der auch die Rauchschwalben Hirundo rustica, Uferschwalben Riparia riparia und Felsenschwalben Ptyonoprogne rupestris zählen. Mehlschwalben erbeuten Insekten ausschließlich im Flug. Sie ernähren sich hauptsächlich von Mücken, Blattläusen, Fliegen, Käfern und kleinen Schmetterlingen und gehören zu den größten Feinden von Stechmücken und anderen Plagegeistern. Während einer Brut verzehrt eine Schwalben-familie mehr als 1 Kilo Insekten - das sind, bei einem Durchschnittsgewicht einer Fliege von 4 mg, etwa 250 000 Insekten. Ihr Lebensraum wird bedroht durch die zunehmende Flächenversiegelung, durch den Pestizideinsatz in der Landwirtschaft und nicht zuletzt durch die moderne Bauweise der Häuser und die mutwillige Zerstörung von Nistplätzen durch den Menschen.