Monday, July 14, 2014

Another successful year for Purple Martins

By Beth Sullivan
Those of you who have been reading this blog for a while have by now realized I am quite fond of (addicted to maybe) my little colony of Purple Martins at the Knox Preserve. In all fairness, they are not “mine” but shared with all who enjoy the Knox Preserve and are a direct result of two Audubon IBA ( Important Bird Area) grants we have received.
Adult male(L) and female wearing bands from last year.
Knox fields, great for insects, great for Martins.

A Flying Snackbar

In the last two years we have managed the habitat at Knox so that the fields are lush with a variety of grasses and flowers that attract all sorts of insects. The aerial insects are what attract the Martins, as they only catch their food while flying. While it is a myth that Purple Martins are great consumers of mosquitoes, they eat all manner of flies, grasshoppers, flying ants, dragonflies and butterflies too. I guess we have to accept they eat some that we actually enjoy ourselves. While doing some research, I discovered that there are literally tons of insect/invertebrates that are caught up in the air column-even those that are not supposed to be in the air! Martins have been seen bringing non-winged ants and other non-flying insects into their nests. It is known that they do not hunt on the ground at all, even when nearly starving!
Since the end of April this year I have been monitoring the two sets of hanging gourd nests. These are equipped with crescent shaped entrance holes that deter starlings. They also have little “porches” on the outside, and in the new set on the inside also, to aid the adults in landing at the entrance and feeding the young. The birds seemed to like the new set better this year, as we had more nests in the newer ones than the set we erected last year.
Over the last months we watched the birds as they constructed nests, by lowering the sets to peek inside. Martins will use a variety of materials depending on what is available. We start them out with clean dry pine needles; they add small sticks and grasses. Several had seaweed/eelgrass, and they often use mud. Once we saw them arranging green leaves, we knew egg laying was near.
We used a diagnostic tool to compare when the first eggs were laid and anticipated when hatching would begin. An average clutch was 5 eggs. The first nestlings hatched around June 19, and continued through June 27, each nest being different. Most often all eggs in a nest hatch at the same time, but developmentally there are some real differences as they grow.
On Wednesday July 9 a team from the DEEP came out to band our birds. Avalonia volunteers joined DEEP volunteers and we met first at Pequot Golf Course on Wheeler Road. They have a very successful and mature colony and have produced over 90 young in 24 nests over the last years. Our nests produced 33 healthy young, and we added another 28 to our tally by including a neighbor’s Martin house occupants! That is considered a huge success for a new colony.

Banded for Identification

It is an amazing opportunity to participate. Each nest is identified with a number. The birds are removed from each nest into marked containers. It is essential that they are returned to their exact nest once banded. Each bird is fitted with a metal federal band with a unique number that will identify it for life. They are then given color bands on the other leg. Our colony has green/orange or green /yellow added this year. With binoculars the colors can be seen and the bird can be identified as from a particular colony. Pequot Golf Course has had blue/orange since last year, and this year I discovered one sub-adult female bird from Pequot had chosen to nest in our colony!
Removing the young and noting the nest number.

DEEP and Avalonia volunteers staff the banding table.

This Martin sports new colored bands.
The young are weighed, and their ages are determined by looking at feather development. Once all is recorded they are nestled back into their gourds, and they settle right in. The parent birds are waiting patiently, their beaks full of food for their hungry young.
This one is about nine days old. The feathers are barely coming in.

This one is closer to 16 day old with much more feathering.

The oldest hatchlings will fledge in another week. Others following suit over time. They will remain in the area, learning to catch their food and often return to roost in their nest gourds for a while. All too soon they will gather and fly south, well into South America, for the winter. We will await their return eagerly next spring and look for their color bands.
Adult Purple Martins return to their own nest, awaiting their young.

We are very grateful for the DEEP team, and all the volunteers that showed up at both sites. Many hands made faster work, and we got a bit dirty, but the experience was surely worth it.

Photographs by Beth Sullivan.  

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