Zwaluwen

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.

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.

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 (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.

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.