Monday, June 13, 2016

Another Purple Martin season has begun

By Beth Sullivan
It is that time of year again-when a naturalist wishes she had a clone to be able to be everywhere at once to observe and enjoy all the changes occurring. There is so much to do: stewardship on preserves, hikes, flowers, gardens, bird watching, horseshoe crab tagging, butterfly counting-the wonderful list goes on and on.
A perfect nest with a layer of green cherry leaves.

This week, the priority is the Purple Martin colony on Knox Preserve.
The first “scout” was reported on April 17. These are usually the fully dark adult males who make the trip up from the south, ahead of the rest to scout out the best locations and sometimes reclaim a good spot from the year before. That was my clue that is was time to get the gourds up.

High rise nests

There are 12 plastic gourds with crescent shaped entrances, designed to encourage the Martins but deter invasive Starlings. The have porches on the outside, and one set has an indoor porch as well. The systems are set up close to each other and close to buildings, as these birds actually prefer to live close to people. Centuries of dependence on humans for their housing has created an interesting bond between people and these birds, and the Purple Martins are truly tolerant of all activity around them.
The Knox Preserve fields are lush and attract insects.

The very cold, wet spell we all endured earlier this spring took a terrible toll on Purple Martins across the state. There were no insects to be found over field or water, and these birds depend solely on flying insects for their food. Many died. One bird, an adult that had been banded at another colony, was found dead at Knox, but I think most of our early birds did okay.
Little by little, activity resumed. Another wave of migrants arrived at the site. The weather warmed, insects hatched and took wing. Dragonflies and butterflies make up a large part of the Purple Martin's diet, as well as insects that get caught up high in the wind columns. The birds all look healthy and strong.

The Knox wetland supplies mud for the nests.
When I lowered the gourds the first time, I was happy to see nests in progress. This week revealed more nests and eggs. Each active nest was strengthened by enhanced by straw, sticks and mud, and all were lined heavily with green cherry leaves. Nine nests had a total of 38 eggs. Several had five eggs-a couple had one, which probably signals that there will be a new egg laid every day until clutch of five to six is complete. Incubation begins when the last egg is laid. The date of first egg laying was between May 30 and June 2 for the first nests, which puts estimated date of first hatchings around June 19 to 21.
From under the gourds, it is interesting to watch the activity as parents build nests.

As I approached the nests, the birds chattered. Yes, I chattered back. None seemed alarmed. They flew off and circled when I lowered the gourds and immediately flew back to them as soon as I raised them back up again. No stress, no dive-bombing.
Mom and dad stay nearby and wait for the nest cleaning to finish. 

More nest visits planned

I will check the nests again within a few days to get a sense of increasing numbers of eggs and to get a greater accuracy of hatching dates. My duties will continue as a nest cleaning occurs when the young are between 10-15 days old to get rid of parasitic mites. Our hope is that the DEEP biologists will return this year to band the young.
We have a few great photographers in our midst, and I hope they will be able to get some better shots that I can share with you as the season progresses.
As soon as the gourds were raised, the parents return.

We suggest viewing the Purple Martins from the trails with binoculars, so as not to disturb other birds nesting in the fields. The ticks are terrible in the tall grass as well. But even from the distance, you can enjoy the Purple Martins' movement and song. I hope you get out and enjoy all that this season has to offer, including the song of the Martins.
This nest had thick straw added to a deep base of mud.

Photographs by Beth Sullivan.

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