[Bluebird-babble] Blowfly evidence in bluebird boxes

[Robin Bartlett]

Kathy, caught your email about blowfly infestation. I am monitor at Cherokee Ranch and have not noticed any undue numbers of pupae in boxes nor chick death associated to blow fly. Usually I see the worst in wet humid conditions with feces compacted nests. That's why I tend to remove those ugly nests and hope the parents will rebuild a clean nest for 2nd broods. Overall, removing the compacted nests usually benefits us with a 2nd hatch. I'll tell you in my 10 years of monitoring I have never ever seen larva on the chick body either. I think the information is true-they come up at nite and attach to legs so as the parents can't pick them off. I do look at chick bodies when conditions are ripe for blow fly and can't find them. We have conducted counts of blow fly pupae per nest and I found when there were over 50 in the nest plug I might see a chick death or more. 

I have associated  increased Diptera concentrations with long wet springs. Bottle or Blow Fly deposit over 1,000 eggs per whack and they need heat and humidity to hatch but just as important they need the manure to lay the eggs in.  What box (type) construction do you have? You could try removing the feces laden compacted nests just after fledge of 1st brood or put pine needles under cleaner nests each time you visit especially after hatch of first brood. The pine resin is a known natural insecticide that's what supposed to do them in or slow them down. Even if blow fly are sucking the chicks blood be aware the chicks are a hemoglobin factory. They can support some insult to their hematocrits. Maybe there is another disease actually killing the weakened chicks? Do you note any whitish areas on the dead chicks? I

If you decide to keep a so so looking nest take a plastic bag  and shake out larvae/pupa. You could also support the nest off the bottom of box with wire mesh...make it harder for the nasties to crawl up to chick. It is the larva you really need to sweep out. The pupa are the last gestational stage for overwintering  or till next cycle whereby the fly pops out and starts all over. That whole cycle takes about 4 to 5 weeks.

I look at the depth of the nest constructed by the BB parents. Generally the thinner ones (around 11/2" to 2" thick) are set ups for lots of fecal compaction and hence the fresher thicker manure for adult flies to lay eggs. Have you noticed some BB parents just can't keep up with the fecal sac disposal system? The BB that can build deep thick nests and work hard to remove the fecal sacs don't have as high blow fly larvae/pupae. If you see nests with around 20 to 25 pupae at end of season bet they won't have chick death from larvae. 

I would advise watching how the chicks look in the box. Do they seem lethargic? Won't raise their heads when you whistle. Seem too weak to take food. When I see that it could be 1) excess temperatures, 2) blow flies, 3) poor feeding by the parents,4) or  disease. I guess you have to take in what conditions your chicks are facing and eliminate those previous options and make a judgment as to cause.

PS If you do remove the first dirty nest I would not advise putting any dried grass in to "help the birds along" with a 2nd nest construction. I believe it 'puts the birds off' and they think another pair has claimed the nest. Then the box never is renested.

Hope this helps, Robin Bartlett
  ----- Original Message ----- 
  From: KathyDressel at aol.com 
  To: Bluebird-babble at denveraudubon.org 
  Sent: Friday, July 18, 2008 10:40 AM
  Subject: [Bluebird-babble] Blowfly evidence in bluebird boxes



  I have cleaned out quite a few bluebird nestboxes on the Winkler Ranch and at Castlewood Canyon State Park.  I have noticed alot of blowfly pupae in the bottom of  at least 90% of those nests.  This is the first year that I have noticed such a huge presence of  this insect.  I also noticed them in the bottom of two of the nests I removed from boxes on my trail in Franktown (Deerfield).
  I know that this was a good year for insects (weather-wise) in our area. I was wondering if anyone else has noticed the presence of blowfly larvae or pupae.  There have been several boxes in which I found dead nestlings.  I think that now I know the cause of their deaths.  I never did see larvae on any of the young, but the boxes are dark and I do not remove the nestlings to really examine them.
  If the weather repeats itself next year, I am thinking of doing preventative maintenance on my three trails.  I will wait until the nests have been built  and eggs have been laid, and then I will place a sprig of pine needles in the bottom of the boxes by gently raising the nest with a putty knife.
  Has anyone else noticed this?  Any ideas?

  Thanks,
  Kathy Dressel



  **************
  Get fantasy football with free live scoring. Sign up for FanHouse Fantasy Football today.
  (http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020) 


------------------------------------------------------------------------------


  _______________________________________________
  Bluebird-babble mailing list
  Bluebird-babble at denveraudubon.org
  http://denveraudubon.org/mailman/listinfo/bluebird-babble_denveraudubon.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://denveraudubon.org/pipermail/bluebird-babble_denveraudubon.org/attachments/20080718/8eaca929/attachment.html