[Tweeters] Lack of Barn Swallows
dennispaulson at comcast.net
Mon Aug 20 11:21:17 PDT 2018
A major three-decade-long study of insect abundance was carried out at a large number of German habitat reserves. This was based on trapping flying insects in Malaise traps. They found a dramatic (75%) and universal decline in insect biomass over that period in what were essentially natural habitats, in other words not from habitat decline at the sites. However, of course habitat was declining in the surrounding landscape as agriculture and development continued. That’s the only rigorously quantified research that I know of. It can be downloaded from the internet here: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185809
Anecdotally, when I lived in Florida there were thousands of insects of all kinds at the lights of every shopping center and front-door light. Now there are few or none in similar situations. There are still warblers, lizards and dragonflies, so they must have something to eat. But coming back to the Pacific Northwest, it seems to me that many different types of birds have declined in this region, the conspicuous exception those that are subsidized in some way by humans—the winners.
> On Aug 20, 2018, at 9:15 AM, Wayne Weber <contopus at TELUS.NET> wrote:
> I suspect that what you say about decline of insects is true, and this would do much to explain the decline of many insect-eating birds (or at least, those that eat flying insects). However-- are you aware of any research into trends in abundance of flying insects in general, or of any species that are important bird food? I have heard of little if any research in this area.
> We have a very good idea of trends in numbers of most songbirds because of programs like the Breeding Bird Survey (in which I am still participating every year), and of waterfowl and seabirds because of annual surveys by professional biologists. However, there seems to be very little info on the abundance of food organisms for songbirds, especially on flying insects. Therefore, although we can say with a high degree of confidence that certain species of birds have declined, and just how severe those declines are, we are reduced to guessing at the causes of those declines.
> If, as I suspect, there has been little if any research into population trends of flying insects, it is a glaring gap in our knowledge which urgently needs to be addressed in the immediate future.
> Wayne C. Weber
> Delta, BC
> contopus at telus.net <mailto:contopus at telus.net>
> From: Tweeters [mailto:tweeters-bounces at mailman11.u.washington.edu <mailto:tweeters-bounces at mailman11.u.washington.edu>] On Behalf Of Dennis Paulson
> Sent: Sunday, August 19, 2018 12:52 PM
> To: TWEETERS tweeters
> Subject: Re: [Tweeters] Lack of Barn Swallows
> Tweets, I agree entirely with Bud on what is probably the major cause of decline in Barn and other swallows. Insects are in decline all over the world, and that has to be one of the most profound environmental changes of our time. The majority of vertebrates eat insects, including freshwater but not marine fishes. Many of them eat only insects. We not only destroy the habitats of insects, but we actively persecute them. As a species, we don’t like ‘em.
> And remember all of our swallows are highly migratory, passing through areas all the way down into South America that may be experiencing similar declines. Pesticides rule in many tropical countries where extensive monocultures of pineapples, bananas, sugar cane, tea, coffee and other crops are grown. Anyone for breakfast?
> Interestingly, in Washington as a whole Barn Swallows are declining but Violet-greens aren’t, according to data from the Breeding Bird Survey. This is statewide, but we all know how much both species have declined in Seattle and I assume other urban areas. I wonder if declines might also be due to loss of breeding sites or nest material (mud and possibly urban ledges for Barn, nest holes for Violet-green). One thing we do in our society is attempt to tidy things up over time, and that could well involve actions that block access to nest sites for swallows. That could even be involved in the declines of House Sparrows and European Starlings that have been so obvious in recent years.
> We are putting up nest boxes for Purple Martins in hopes of bringing their populations back up to the numbers of decades ago. I wonder if we should be thinking in terms of nest sites for our other urban swallows.
> Dennis Paulson, wannabe hirundologist
>> On Aug 19, 2018, at 12:00 PM, tweeters-request at mailman11.u.washington.edu <mailto:tweeters-request at mailman11.u.washington.edu> wrote:
>> Date: Sat, 18 Aug 2018 12:21:13 -0700
>> From: Bud Anderson <falconresearch at gmail.com <mailto:falconresearch at gmail.com>>
>> To: tweeters <tweeters at u.washington.edu <mailto:tweeters at u.washington.edu>>
>> Subject: [Tweeters] Lack of Barn Swallows
>> <CAN4Y+ROUWpgqZSxhEQq_OPFG7Erjk9RvQ1+pov30m3M1qZniBQ at mail.gmail.com <mailto:CAN4Y+ROUWpgqZSxhEQq_OPFG7Erjk9RvQ1+pov30m3M1qZniBQ at mail.gmail.com>>
>> Content-Type: text/plain; charset="utf-8"
>> I have been watching late summer swallows at Sea-Tac on an incidental basis
>> since 2001, enjoying the large numbers of family groups that used to
>> congregate on the west side perimeter fence each summer. I always looked
>> forward to their pre-dispersal numbers. I estimated this annual mixed
>> species swallow flock to be in excess of 1,200 birds.
>> However, over the years, this number has decreased markedly and I doubt
>> there are now more than 100 that gather there anymore. I will make sure to
>> count them this week.
>> Even here on the Samish Flats, there are far fewer swallows than normal.
>> Like you, I find it incredibly depressing to even think of the possibility
>> that we could lose our swallows.
>> As to causes, I think one of the most logical avenues of thought would
>> involve the famous decrease in insects that is being reported these days.
>> Maybe we could hear from any swallow biologists out there.
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