Problems /Solutions with Blowflies in nests (Part 3)

In addition to Messages that have appeared in the Bluebird Mailing Lists on this topic, the following are on the Audubon Society of Omaha website: 

• Predators and Problems On The Bluebird Trail
• Biomonitoring With Bluebirds
• Blowfly Research

Terry Whitworth's Blowfly web site

From: Steve and Cindy Groene [mailto:hausgroene"at"comcast.net]
Sent: Saturday, June 24, 2006 8:39 PM
Subject: flies in BB nest and cedar waxwing

I removed the nest from the nestbox after my 4 EABL chicks fledged and put it in a ziplock bag. That was four days ago. This evening we came home and the ziplock bag w/ the nest that I put in the garage has flies in it. They look like regular flies rather than blowflies. Are these, in fact blowflies? I never noticed larvae in the nest. I also never picked the chicks up. Should I have been picking them up to examine them for flies?

Cindy Groene
South Lyon, MI

From: denisefarmer"at"comcast.net [mailto:denisefarmer"at"comcast.net]
Sent: Saturday, June 24, 2006 10:14 PM
Subject: RE: flies in BB nest and cedar waxwing

Cindy,

Below is a link to pictures of blowflies,, check it out and see if they look like your flies is my best advice

Denise
Parkville, MD

http://www.nabluebirdsociety.org/blowflies.htm

From: Bet Zimmerman [mailto:ezdz"at"charter.net]
Sent: Sunday, June 25, 2006 10:48 AM
Subject: RE: blowflies in BB nest

Cindy wrote: I removed the nest from the nestbox after my 4 EABL chicks fledged and put it in a
ziplock bag. That was four days ago. This evening we came home and the ziplock bag w/ the nest
that I put in the garage has flies in it. They look like regular flies rather than blowflies. Are
these, in fact blowflies? I never noticed larvae in the nest. I also never picked the chicks up.
Should I have been picking them up to examine them for flies?

Hi Cindy - Basically yes, the adults look like houseflies. Usually we just see the larva
(disgusting white/gray fat maggoty things) or pupa or pupal case (brown) in the nesting material or
sometimes attached to a baby bird. When the larva are really small (before major blood sucking)
they are about the size of a grain of rice.

http://www.purplemartin.org/update/Parasites.html has a picture of an adult Blow Fly. There are
more pictures at Terry Whitworth's blowfly website here http://www.birdblowfly.com/ but the photo of
the adult is kind of small.

It is a good idea to check the nest for blowfly larva after nestlings have hatched.

>From great links and resources: http://www.sialis.org/forumlinks.htm#blow

The earlier these larvae are found and removed, the better for hatchlings and nestlings. Sometimes
by gently rubbing through the 'dust' on the box floor under the nest, blowfly larvae can be felt
before they can be seen (they really blend in with the dust).

A major infestation of blowfly larvae (>10 per nestling) may require nest replacement. This may need
to be repeated for the same nesting as new blowfly eggs are laid and hatch in as little as 36-48
hours. Moving the baby birds from the infested nest to the replacement nest can be dangerous to the
baby birds' soft bones, so do not "roll" them. Nest change instructions:
http://www.sialis.org/nestchange.htm

Try using a hardware cloth screen (3/8" square mesh [rabbit cage size] in a squared "U" shape or
slid into slots in the insides of the box) to keep the nest about a half-inch off the box floor.
Debate about these screens includes concerns that by the time the larvae are heavy enough to fall
out of the nest and through the screen, they've done most of their damage to the baby birds.
However, they do make it easier to sweep out larvae and will help keep the nest dry. You may want to
put the screen in AFTER the nest is built to prevent pushing material down through it during nest
construction.

Low-level (0.03 - 0.1%) pyrethrin pesticide can be used under the nest. However, this is a toxin and
is considered a last resort.

Put crumpled bay leaves in the bottom of the box (I have no idea whether this works.)

Bet from CT

From: DrDodson"at"aol.com [mailto:DrDodson"at"aol.com]
Sent: Friday, July 28, 2006 4:18 PM
Subject: blowflies

Can anyone tell me if blowflies are a problem in Missouri? I am new to bluebirding. So far I have not seen any evidence of blowflies. I would like to know what their range is. Thanks Jack

From: roy pischer [mailto:tlp4456"at"msn.com]
Sent: Friday, July 28, 2006 5:24 PM
Subject: Re: blowflies

Jack, I have never had a problem with blowflies, but I'm fairly new to bluebirding. Lawrence Herbert from Joplin is way more experienced than I and will surely answer your question. What part of Missouri are you in? Now Black Snakes, HOSP and Paper Wasps I can tell you about... Ugh....

Trudy Pischer
Willard, MO

Bluebirdsters: Sorry, but I know very little about blowflies in bluebird houses in Missouri.

A study done in about the nesting season 2001 found them in 3 of 60 nests, or 5 %.
I suspect that over time and seasons that they would be closer to 10 % occurrence here in Missouri and Kansas. Rarely (about 1 in 150 nests, or so) are their numbers up so high in the nest that they are obviously detrimental to the developing nestlings (pers. obs.).
I am speaking for just this area now. I have heard that they are much more of a problem other places around the country.

Blowflies resemble those green bottle and blue bottle flies that are so common around manure and carrion. Same family I'm sure: Calliphoridae.

Here's one way to determine how abundant they are in your nest boxes:
As soon as the nestlings have fledged collect the nest and place it in a sealed zip loc type bag. The critters will emerge anywhere from one day to two weeks. You'll find all kinds of mites in there also!

Good birding, Lawrence Herbert, Joplin (sw) Missouri.

From: MJ Shearer [mailto:eshearer"at"comcast.net]
Sent: Tuesday, August 01, 2006 8:56 AM
Subject: Re: blowflies in MO.

Here's a link to Dr. Terry Whitworth's blowfly web page that provides photos and blowfly information he collected during his research on nest parasites.

http://www.birdblowfly.com/

MJ

Mary Jane Shearer; Tucker, GA

From: Lawrence Herbert [mailto:lherbert"at"4state.com]
Sent: Friday, May 11, 2007 4:13 AM
Subject: parasite research

Anyone collecting the old bluebird nests for parasite research?
I'm willing to save and send for the mailing labels.
Larry H. Joplin (sw) MO.

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