My efforts for blowfly larvae control in nests have been successful, until quite recently. This set of larvae were so strong and in large numbers, the nestlings became too anemic and weak to survive the amount of feedings they were ingesting from Mom and Pop Blue. They were 9 days old when death came knocking at their nestbox door. The last time I lost a whole brood to blowflies was Spring 2008. Not all happenings on the bluebird trail are happy ones. I will continue my two methods of control: (1) hardware cloth bases below nesting material (helpful but not as effective as the only method of control) and (2) the use of puffing some organic food-grade Diatomaceous Earth inside the center of the nesting material and underneath the nest on the wood floor of the nestbox before bluebird eggs hatch. The key is to eradicate the larvae while very young, right after they hatch, which nature usually times around the same time the birds’ eggs hatch. I had treated this nestbox with the DE, like I have all others. This year and at this nestbox, I must not have applied the right amount of the DE to take care of the number of hatched larvae to cause the damage they did. Below are a set of photos of different methods I’ve used in past and presently (applying DE) and another method of using leftover hardware cloth from making the Noel Guards for my boxes for the bases to slide underneath completed nests. Captions will explain the pictures. Warning: The last photo in this series is not a pleasant one. I cropped out the dead bluebirds, but I wanted you to see the larvae that killed this brood. You will note how large the larvae got, some gorged with blood, and a dead bumblebee–which obviously was the last-ditch effort of feeding the parent birds attempted to make for their 8-day old kids, too weak to eat. This is a good representation photo of what the larvae looks like when healthy and successful feeding on the nestlings at night. I had to dissect the pine needle nest to find this big patch of them.
I put a clean washcloth on top of nest with eggs. I use a mustard/ketchup type squeeze container with tip and insert a few puffs in three sections inside the center of the nest. THIS IS DONE BEFORE HATCHING.
I then repeat a few puffs underneath the nest material on the bare wood floor. I use the metal paint scraper to gently lift the nest up to apply. Note the clean washcloth remains on top of nest. This keeps any DE powder off the top of the nest.
I keep the box open for a minute to let any DE powder settle. Before I remove the washcloth, I use a clean paintbrush to remove any powder residue from the sides of the nestbox. THEN I peel back towards me and out the washcloth, close and secure the box, and quickly leave the nestbox area.
I’m making bases made of leftover hardware cloth from the construction of the Noel entry-hole guards. I use tin snippers to cut and shape to fit the inside of a nestbox. These are slid in an already completed nest. If this can be done after nestcup is completed but before eggs are laid, that’s ideal. If not, you can slide it in after the eggs are laid, but be gentle!
I’m experimenting with one-half inch off the nestbox floor AND one inch off the nestbox floor. This pictures shows a tad higher than one-half inch.
This is about one inch off the nestbox floor. I am finding I like this much better. I can always remove some of the nesting material if it brings the nest up too high close to the entry hole. Also it allows easy brushing out of blowfly larvae when it’s an inch off the floor.
Here is an active bluebird nest with the one-inch high base. I slid this in a nest with eggs. I also applied a thin layer of DE to the bottom of the box. Look closely; you can see the eggs! This box fledged baby bluebirds.
You’ll note dead bumblebee–brought in by the parents but not eaten by the nestlilngs. Larvae are plump, some gorged with blood. This larvae killed 8 and 9 day old bluebird nestlings.
Hello- I am a backyard Bluebird Monitor in Central Virginia and lost four 9-day-old BB chicks in 2010 due to blowfly. I asked local BB folks, tried a recommended systemic tick spray in empty boxes and in nest before eggs were laid, with little success, yet fledged five nestlings this year in two cycles. I want to share my nesting material story…
I have a new suggestion for monitors: I read that pine needles seem to be the ideal material for blowfly, so when I discoverd them in the first pine needle nest, I destroyed it (burned it) and built another from the cocoa lining found in planter boxes and hanging baskets. This I did when nestlings were nine days old. Neither Mama or chicks minded the switch. The next day I noticed that the chicks were getting their nails hung up in the cocoa, so I took a bunch of raffia (found in crafts stores), cut it into 2 inch strips, and lined the nest over the cocoa. The nestlings liked this and successfully fledged. They actually had more room in the box during especially hot days. I found no blowfly larva in the cocoa material. It is spotless. This cocoa material is cheap and can be found in any garden center. Try it.
Good luck with your season. Diane
Hello, Diane. Thank you for sharing here. I do not use any pesticide-type sprays in any of my nestboxes. The blowfly lays eggs in birds’ nests, and the bluebird gets hit hard by these in nestboxes, in certain areas. I have this issue chronically in just about every brood. This year, the blowflies arrived later than usual and laid eggs in nests later than usual. My first two broods this year were much lighter in larvae. However, third broods are particularly strong this year on my trail. The organic food-grade diatomaceous earth never touches the birds the way I apply it. It is a safe solution for a trail as I’m limited in natural clean-nest material made by bluebirds. I do save clean, unused nests (such as when a female is killed and thus the nest is abandoned or the eggs go missing). I used to do nest switch outs early on, particularly when I only had one nestbox. I have plenty of clean, natural white pine mulch on my own grounds, so I can also create pine needle nests from that. I do not buy manmade materials to use for nest switch outs–do not have to. I appreciate you sharing what you have on the availability of this in emergencies and am glad it helped you during your situation. That is good to know! I have a blowfly problem in ALL nests, not just soft or coarse grasses or a mix of pine needles and grasses or just pure pine needles. As a matter of face, the brood of 4 I just lost, in spite of effort for blowfly deterrence and treatment, was all pine needles–I took photos of the amount of blowfly and many gorged with the nestlings’ blood from the night before. I did post that picture on a recent post. However, since I treat all my nests, needles or grass, with the DE, that is my biggest treatment that works for me year and after year. ONLY this year, have I seen a stronger, more robust set of blowfly larvae surviving my treatment. Since, 2008, I’ve lost ONLY one brood to the larvae since my treatment program–and that was recent (this season in July 2012). I can attest that some very tight grass nests were packed with dead blowfly larvae from my treatment upon cleaning out a nest that fledged baby bluebirds, so both grass and pine needle nests are hit by larvae (at least for me). The blowfly female looks to lay her eggs in a birds nest in general–those blowfly larvae hatch on or around the same time as the birds eggs hatch. I have now found it is important that I treat all nests right away, on or around the time the female creates her cup and as soon as egg laying begins. I find the DE is even more powerful in eradicating the larvae after they hatch and while still very small. You are correct–the bluebirds are quite tolerant of us intervening. Isn’t that a wonderful thing, too! I’m not sure about cocoa mulch. One reason why I shun it is I know it can be toxic to pets if they eat it, so I would be one probably not to try it. We monitors care so much and do what we can to help the bluebirds succeed in fledging their babies. Thanks again for sharing what has worked for you.
Cocoa MULCH is not what I used. The cocoa or coir is a hemp-like material used as the liners for hanging planters. Sorry for your BB loss. Not convinced about DE, and will be more vigilant about monitoring and burn infested nests and create new. Check out my blog to see the actual nest material I used.
Will do, Diane! Noted correction.
This is where I learned about DE use in nestboxes for blowfly control. Mr. Schmeider gave a presentation at the NABS conference in Fall 2009 in Grantville, PA, about the fledging experience. This is what he uses in his nestboxes to control blowfly larvae taking out nesting baby bluebirds, and that is when I started to do the same method, which has worked for me. I cannot conduct that many switchouts of nests on my trail since every nest–every brood has the larvae issue. Thanks again for your comments. I always support people who have methods of success. http://livingroomtunes.com/newambassador/?p=18