Sunday, July 1, 2007

Purple Martin Nest Changes

The Purple Martin Conservation Association (PMCA) and the Purple Martin Society (PMS) both advocate that landlords do nest changes when the nestlings are 10 and 20 days old, and if a nest becomes excessively wet or soiled. This is for parasite control, especially for mites and blowfly larvae, since large infestations of either can weaken or kill nestlings. Landlords with large and super (over 100 nests) colonies generally aren’t able to do nest changes, due to the time it takes, and some of them use Sevin dust sprinkled into the nests for parasite control. Both of the above organizations discourage the use of Sevin, although you will find many successful landlords who endorse its use.

I am personally opposed to using Sevin or other chemicals on my property, so I have chosen to do nest changes. I changed my first 3 nests of the season on Thursday, and did an additional 5 nests today.

These are photos of my supplies:

For all my nest checks, I have a small flashlight and a telescoping, angled mirror (from an auto parts store) for inspecting nests. I have a wooden chopstick, for gentle probing into nests to uncover eggs that might be hidden or to separate newly hatched young so I can count them. I have my laminated sheets from the PMCA with life-sized photos of young, in order to age them properly. I also have my digital camera and a pair of gloves so my hands don’t slip on the pulley rope. Finally, I have a data entry sheet, although I usually record my findings on a legal pad and transfer the data after I finish.

When doing nest changes, I add the following: A variety of clean, dry nest materials, including (clockwise from bottom left): pine straw (dry white pine needles), cedar chips, and dry grass clippings from my (untreated) lawn, and a small bucket or a plastic pet food bowl for putting the young birds in while I clean the gourd and replace their nest. When they are older and more active, I will use the green 5 gallon bucket to hold the young, so they can't get out.

I also take along rubbing alcohol, paper towels or clean rags, diatomaceous earth (DE) and a trash bag for old nesting material.

I carefully remove the young from their nest and place them in a container with dry grass or cedar chips, covering it to protect them from the sun while I change their nest. I put all the old nesting material in a trash bag and look inside the gourd for wasps, wet spots, or other problems. I use alcohol to wipe out the insides of the plastic gourds. I don’t bother to use alcohol in the natural gourds, because the inner surface is so rough, mites could easily hide from the alcohol wipe.

When replacing the nest, I put a small handful of cedar chips in the bottom of the gourd, then in the larger plastic gourds, a small handful of pine needles. On top of that, I add some soft grass clippings, forming a nest cup in the back of the gourd, and replace the young. In the natural gourds, which have less room inside, I use grass clippings only.

This group of 5 Purple Martin chicks are undergoing their 10 day nest change, which I did last Thursday. Note the chick in the center of the photo. You can see it looks lighter in color than its siblings. It is the last hatched of the clutch and is 1 to 2 days younger than its nest mates. You can see the feather tracts clearly on the runt and the emerging pinfeathers on the wings and tail of the older chick to its right.

Two of my natural gourds were damp on the bottom, and in those two, I sprinkled some DE before I added the cedar chips. I will tell you that both DE and cedar shavings are very controversial among martineers. DE consists of the microscopic shells of tiny crustaceans, and is purported to cut the soft bodies of slugs, bugs, and other undesirables in the garden. As a “natural” product, its use is recommended by those who are anti-chemicals. The anti-DE crowd says that the fine particles of DE dust in an enclosed gourd or bird house could cause lung disease in the nestlings. I don’t know which is right, which is why I reserve DE for natural gourds that have wet spots only. I figure there will be less dust blowing around this way. Mites are attracted to wet spots, but DE is less effective when wet, so maybe I am not doing any good with this approach.

Cedar shavings are also controversial. The aromatic oils do have some insecticidal properties, but again, might cause lung disease. The PMCA position paper has not found any harm in using cedar shavings, but if I remember correctly, the PMS is against using cedar. I have chosen to use it, but this might be a bad decision. Whatever you decide, remember that “natural” does not always equal “safe.”

People often worry that doing a nest change might cause the adult birds to abandon their nests or might be disruptive to the young. Here is the brood of Purple Martins from the previous photo today, 3 days after their nest change. You can see they are growing and thriving. I couldn't even recognize the runt, although I did not take them out of their gourd for close inspection.

Nest checks on 11 gourds and nest replacement in 5 of them took me 30 minutes. The adult birds flew around and complained while i was working, but went right back to feeding and caring for their young when I finished. It is pretty neat to be so intimately involved with these birds and to watch them develop.

One gourd that had 4 unhatched eggs last Sunday had 2 new eggs on Thursday and 3 more today, for a total of 5 in the re-nest attempt. Originally, this gourd was occupied by an SY (Second Year or Subadult) pair, but during my observations this week, I have seen an ASY (After Second Year, of Adult) male attending this gourd. I don't know if it is the same female or not, they are harder to tell apart, but at least the male is new. I have a Cooper's hawk hanging around, and about a week or 10 days ago, it caught something - maybe that male SY martin.

Here is the re-nest in Gourd #22:
This is a great shot of a martin nest, complete with a mud dam, green leaves lining the nest bowl, and 5 eggs. In this view, the 2 1/4" round entry hole is to the left of the photo and I am shooting through the 4 inch diameter access hole, normally closed with a screw cap, but opened for inspection.

Finally, a non-martin photo:

This is a bluebird nest. For me, finding a bluebird nest isn't too unusual, but there is something extra-special about this one. It is the third nest of the 2007 bluebird season, and marks the first time in 15 years of bluebirding that I will have a third brood in one year. So far, this pair has produced five fledglings from the first nest and six from the second. I saw one of those fledglings just today, along with Papa. I hadn't even noticed nest building, but when I peeked in the box, I found this completed nest. Whoo-hooo! Bring it on - more bluebirds!


nina said...

This is really interesting information.
And speaking of being "intimately involved"--I feel very excited about my nesting phoebes--but have a question you might be able to help with.
I know there is a time as the young get older that you should not open the boxes to check them or they'll prematurely jump.
I can now see that I (she) has 4 very alert babies peeking over top of nest. If I approach to take a picture, will they bail? (I don't want to disturb them, yet have them almost literally under my nose--can I do it?)

KGMom said...

Isn't that interesting--we use DE for our pool filter!
I love bluebirds and have only seen them here rarely. I think our area is too suburban. Not enough open spaces.

KatDoc said...


I haven't monitored Eastern Phoebes in the nest, so this is speculation.

With Eastern Bluebirds, the time from hatching to fledging is 16-21 days (mine usually go about 18 days) and I never open the nest box after 12 days. I read this somewhere, but can't remember the source, maybe the Stokes' guide to bluebirding.

According to the Cornell Lab of Ornithology's "All About Birds" website, Eastern Phoebes fledge in 16 to 18 days, very similar to bluebirds, so I would use the same guidlelines about approaching too closely, with 12 days as the cut-off point.

On the other hand, phoebes do seem to be very tolerant of humans in proximity to their nests, sometimes raising a brood near a back door that opens and closes constantly. Audubon was even able to band one in the nest in 1840 and demonstrate its return the following year.

Perhaps if you have a long camera lens, a tolerant phoebe family, and if you move slowly and cautiously enough, you could get some good shots.

Hey, Zick - you are our phoebe expert. Do you have an answer for Nina?


nina said...

Kathi, you're right about her being fairly tolerant of our comings and goings--she chose this spot, after all, right above the grain cans we open every morning. But she's failed twice at raising them to hatchlings--raccoons--and I'm tossed between being so very wanting to capture her success, yet not wanting to prevent it.

Susan Gets Native said...

You are, as you stated yourself once, "anal retentive". but look at all the baby "bewds" you get! Doing something right, I think.

Jayne said...

Just fascinating Kathi! Thanks for the "bird's eye view" of your nests! I am also enjoying seeing the third nest of my bluebirds. They had four the first brood, five the second, and last check, there were four eggs in this third nest.

Susan said...

I have worked at 2 wildlife rehab centers in FL and have used DE at one center and for my home. There are 2 types of DE. The most common is sold for pool filters and has been heat treated and chemically processed. It can be harmful to animals. The best type is the food grade DE. It is registered by the EPA and labeled for insect control. It has been used for years in the food processing industry to treat stored grains to eliminate insect infestations. Food grade DE is used by many zoos to control peats. It is even safe for animals to injest in small doses to kill internal parasites, however the dust can be harmful to the lungs.

Anonymous said...

i like to check pig