Purple Martin Update...April 28, 2006

[Steve Kroenke]

Purple Martin Update?April 28, 2006

My second year round hole purple martin colony continues to flourish and more SY martins are still arriving daily to claim territory. Though the number of new martins is gradually slowing now, I still can expect to gain more occupants into late May. In 2005, I attracted about 20 pairs of martins during May.

My last update was posted on April 18 and I had about 130 pairs of martins in residence. Well, as of April 28, 2006, I have around 150 pairs of martins give or take a few. Large numbers of SY males are seeking territory and mates and these martins are competing with the established residents. Some of the permanent ASY martins continue to try to hold more territory than their nest cavity and the new SY males are challenging these dominant ones. Just today a persistent pair of SYs finally took a large natural gourd that had been dominated since mid-February by an ASY male. The SY males win some and lose others, but they are still slowly managing to gain a foothold into my colony. Unfortunately, the SY males will probably soon start committing infanticide behavior by throwing out new hatched unprotected baby martins in an attempt to secure territory and mate. I observe this phenomenon every year and I am sure it will happen this season.

I have studied purple martin biology/behavior for over 40 years, beginning as a young 11 or 12 year old boy. Never have I seen so many martins or experienced such phenomenal growth with any of my previous colonies in north Florida. This area of northwest Louisiana has a huge density of breeding martins and I do believe we are on a major migratory flyway for many songbirds and raptors. For my first season (2005) in Louisiana, I attracted a whopping 81 pairs with 76 successful and it appears I may nearly double that number in 2006.

My next door neighbor, Bob, has about the same number of martin pairs so our combined two colonies have around 300 pairs as of April 28, 2006. This total will no doubt increase by the end of May. Bob and I have been discussing the impact of such a large concentration of martins on the food supply! If we end up with around 350 pairs of martins with an average of 4 babies per nest, then that means there will be about 1400 mouths to feed from the first of May to possibly late July. Since martins feed their young primarily large prey, particularly dragonflies, unimaginable numbers of these ?meaty? invertebrates will need to be available. Dragonflies breed in ponds, lakes and other bodies of water. We do have many small ponds (for cattle) located in this area and the Sabine River is about 8 miles south of us. Last year we had almost drought conditions and many of the small ponds either dried up or were extremely low. This did somewhat adversely impact the dragonfly population as the numbers of them brought in by the martins to feed their young were smaller than usual. However, we did not see any negative effects on the martins. If a major prolonged drought was to hit our area or other locations, then martin colonies with many young could possibly be hurt. Some questions to think about. How does drought impact dragonfly dependent birds like martins? Can there be too many martins concentrated in a location that may exhaust the availability of a specific food item like dragonflies which are dependent of bodies of water to breed? Are dragonflies sufficiently mobile to fly long distances and disperse over a wide area? I am interested in the concept of ?carrying capacity? of a specific location relative to the availability of flying insect prey and the number of colonial aerial insectivores like martins that can survive and successfully breed.

My natural gourds that maximize vertical/horizontal depth are proving to be the most popular cavities, showing that martins like to be out of sight and out of reach of ?things? from the outside! Depth can be defined as a hole that is cut vertically farther up from the nesting chamber to create a woodpecker like cavity that served (and still does out west) martins well in the past. Or, depth can be largely horizontally with the entrance cut on a gourd neck that produces a narrow funnel/tunnel foyer area with either straight line entry or an offset angle with the offset configuration creating the most seclusion. Both vertically and horizontally deep cavities create a nesting chamber environment that greatly protects the martins from predators and helps keeps their young out of view from the ?dangerous? entrance hole. I will soon present specific statistics on martin occupancy levels of my various cavities.

My Troyer horizontal plastic gourds are proving to be almost as popular as my comparably shaped naturals and I plan to use many of these excellent substitutes in subsequent seasons.

The PMCA Deluxe gourd racks that I added cane perch poles to increase perching space are being heavily colonized by martins. The additional perches are used all the time by the martins and give the more timid SY males a chance to approach a potential nest site cautiously. Next season, I will add more perching space to ALL my Deluxe gourd racks.

The female martins are laying MANY eggs and a number of full clutches are being incubated. Egg totals are dynamic and change daily, but there are over 500 eggs so far with more to be laid. I am seeing many 5 and 6 egg clutches. I would suspect that around 800 eggs will be laid in total.

Starlings and house sparrows continue to be almost non-existent at our personal colonies. I shot one male starling in February that was flying around our colonies. Then in April I shot a male starling that made the mistake of landing on a utility line near my house. So two starlings is not a big problem and can be easily controlled permanently through shooting at the present time. A male house sparrow showed up in early April and often sat in the top of a small pecan tree in Bob?s yard. The sparrow never visited our martin housing and just sat there and chattered, probably calling for a mate. Well, one day he arrived when Bob was home, I notified Bob, and he shot the sparrow. No more starlings or sparrows with our efficient system of permanent control.

The major threats to our martin colonies are migratory Accipiters and merlins and resident Cooper?s hawks and barred and great horned owls. Merlins have been particularly active this year attacking our colonies and one day I observed 7 visits/attacks. All were unsuccessful because of my intervention, the openness of our sites and the martins? superb flying abilities. Accipiters have tried a number of times and were only successful twice that I observed. The main effect of the merlins and Accipiters on our martins has been ?psychological? by producing ?hawk fright? behavior, particularly early in the nesting season. Resident Cooper?s hawks will most likely predate large numbers of martin fledglings in June and July just like they did in 2005. Owls, mainly great horned, will probably become a major predator of any outside roosting fledgling martins during June and July. So for our colonies, it is the martin fledglings which suffer the greatest amount of predation.

All our martin housing is protected from rat snakes with net traps made from bird netting. Amazingly, we did not catch a single rat snake in 2005! In 2004 I believe Bob caught several large rat snakes in his netting. I caught rat snakes all the time in my net traps when I lived in north Florida. I don?t know if we will have a rat snake problem in 2006.

Male martins are reducing their dawn singing activities now as April is almost over and many female martins are incubating full clutches of eggs. However, some males will continue to dawn sing almost through May. The early morning nocturnal vocalizations, such as the territorial/mate reinforcement gurgling call, which are common earlier in the season, are diminishing, too. As the males become more ?family oriented? and start guarding full clutches of eggs, then the instinctive drive to protect territory from rivals will weaken. The males tend to stop dominating multiple cavities and spend more time guarding their nests.

The violent sexual attacks on the females by gangs of primarily ASY males are also diminishing. Thank goodness! With many of the ASY females now incubating eggs, they are no longer ?good? candidates for copulation and the males largely ignore them. However, there are still new pairs forming, particularly SY martins, so as long as non-incubating females are flying about ?presenting? themselves either intentionally or not, then rapes will still occur. These females can be mated and the males can spread their genes. The violent raping of female martins by gangs of ASY males is more common in large colonies. I rescued a number of females this year after as many as 10 ASY males knocked them to ground in wet grass and repeatedly raped them. The females couldn?t fly because they were wet and totally exhausted. They were vulnerable to Accipiter hawks, cats and rat snakes. Some were in foot tall grass in hay fields and I am not sure if they would have ever been able to get out. It would have taken a while for their feathers to dry and for them to gain strength to fly. I took them inside dried their feathers with a hair dryer, let them rest for about 30 minutes, and then released them.

I am looking forward to May and seeing if more SY martins will be able to establish territory in our colonies. We are having a fantastic purple martin season in northwest Louisiana. Hope everyone else is doing great, too.

Stay tuned for more updates.

Steve

[Donnie Hurdt MN]

Thanks for your report Steve. It is always intersting to read the result of your work. So far this year I havent had much trouble with starlings or sparrows. I think that the survivors learn to stay away and not bring others in. I have so far shot 4 starlings and no sparrows since this past winter. Not that I am complaining, the peace and quiet is nice compared to other years.
I just need to convince a kestrel that my housing is not perfect place to perch and maby I will get a few visitors.

[floridasunshinegoddess]

Steve, I have been watching with much interest as your colony has rapidly, more like, EXPLOSIVELY grown. You surely must be on a main migratory path..... But then, you do everything right too. Your success was inevitable.

I appreciate all your wonderful reports and updates.

The Dragonfly issue is something I've thought about too. I have been watching (6) nestlings with a nest cam and it has amazed me just how many Dragonflies the Martins feed them. We're having a drought in Florida and I've wondered about the continued supply. Fortunately we have a lot of lakes but suppose the drought was very prolonged. I'm sure it would have a negative impact.

Keep up the good work and give us another update real soon. Can't wait to hear the totals at the end of your season.

[Steve Kroenke]

Hey DhurdtMN,

Thank you for keeping those starlings and sparrows under control at your house! The kestrel would keep any martins from investigating your housing. Though the kestrel is not a big threat to adult martins, it is still a raptor and martins would view it as a danger.

Steve

Hey Barb,

Thanks for the nice words! More SYs arrived today and we still have most of May.

We had a nice rain today and we needed it. I am seeing dragonflies and two clutches of martin eggs have hatched. The parents are bringing in small insects initially, but that will transition into dragonflies very soon.

There are so many lakes in central Florida to raise millions of dragonflies! So I believe your colony would do well even in a drought unless those lakes dried up.

I will keep folks posted about our colonies in northwest Louisiana. Please keep us posted about your great colony, too.

Steve

[Davlyn]

Hey Steve, I truly can not imagine that many martins at one time!! I think
I am going to get the extension for my deluxe gourd rack this winter, and
after reading your thoughts on the Troyer horizontal plastic gourds I think
I am going to go with six of them. Right now I have 8 natureline gourds
and 4 natural on this rack so with my extension I am going to add 6 more.
So I am going to get six of the Troyer gourds.
The only trouble I have had so far is the cooper will show up on occasion
but he has not been successful as of yet! And a few days ago I looked out
and there was a male house sparrow on my trio house as soon as I
walked out the back door he flew off, I have seen him in my maple out
back I am sure he is one from next door because he will fly away as soon
as he sees me. I just hope that he will go in my trap door on the house if
he comes back while I am away, I am a little worried about it! But other
than that everything is going great, I have three females feeding young
and five females on eggs! Love reading your post and glad to hear that
your colony is doing great, keep us posted.

[Steve Kroenke]

Hey April,

I am pleased your martin colony is doing well! We have resident Cooper's hawks over here, too, and they are just waiting for martin fledging time. Then the hawks will start predating the youngsters. Merlins are still coming through and we had two unsuccessful attacks yesterday. These falcons fly like jet fighters and will tail chase martins for long distances at times!

Please try the Troyer horizontals. They are my favorite plastic gourd and the martins are really taking to them at my colony.

The house sparrow can be a problem if he sneaks into a martin nest with eggs or very small young. Try to trap or shoot him ASAP.

SY male martins are still arriving in good numbers at my colony and I am sure I now have more than 150 pairs of martins. When I complete more thorough nest checks a little later in the season, then I will have a better picture of the exact number of martin pairs that are in resident.

Please keep us posted on your martin colony. Continued great success.

Steve

[Flylow]

Hey steve send some of those SY up to Indiana.