|The adults declare territory |
and build nests.
This year started slow. Our purple martin colony at Knox Preserve seemed to take a long time to get occupied and established, but, once it got going, it was amazing!
It was late April when the first scouts arrived on the site, but it was into May before there were others coming in to make their happy chorus. The songs of happy purple martins are unmistakable. Chattery and bubbly. As the month of May progressed, the adults were busily constructing their nests. Each year when I set them up, I put a nice layer of dry pine needles into each gourd. A little welcome mat. It’s always interesting to notice the difference in the follow up techniques though. Most martins use moderately thick grass stems, some work up to straw blades, and then others carry in small twigs. In some years, the birds will actually bring in mud to reinforce the nests. Some have speculated that it may help insulate the nest. So far this year, there was no mud used in our colony. The nests are pretty neat. If I discover a really messy nest that fills up the entire gourd, I know it is a house sparrow and remove the material to discourage nesting. House sparrows are invasive and will fight and even kill martins (and blue birds and tree swallows) to get access to favored nesting sites. This year it seemed that the martins got the upper hand and once I evicted a couple of sparrow pairs, the martins were quite effective at defending their territory. By the first of June, most nest building was complete. A sure sign that egg laying is imminent is a lovely layer of green cherry leaves that line the cup of the nest. Some birds bring in just a few, others are quite enthusiastic in their layering. There is some thought that cherry leaves help deter or kill parasitic mites that can harm the young.
|A perfect nest lined with green leaves|
and filled with five eggs.
Once egg laying begins, the female will lay one egg a day, at sunrise, until her clutch is complete. Average is 5 eggs but this year we had one with 7! Each week we checked the nests and counted eggs. There is a formula to use to calculate when eggs will hatch based on when they are laid. Most of the clutch hatches in one 24-hour period. Once in a while a random female will ‘dump’ an egg into an established nest. Sometimes it works out quite fine. Sometimes they hatch much later, and the young bird is quite handicapped by its smaller size in the nest and feeding position and it will not survive.
This year promised to be the best in our 9-year history. At the highest count we had the potential for about 87 young and eggs were still being laid! As in other years, some of our birds started early nests, while other pairs were late starters. There would be quite an age span as we started our monitoring over the next phase.
|So wonderful to |
share this experience!
Things were going well until that last few days of June when we had the terrible heat wave. That was followed by the sudden drop in temperatures, into upper 50’s with rain for several days. It is impossible to know what was worst: the heat, the cold or the rain. In cold rain there are no insects flying and the parents couldn’t support their rapidly growing young ones.
Today, July 5th, I was able to get out and check the colony. I was fearful of what I might find. The first set of gourds seemed to be ok. A few birds seem weak or thin but were alive. In the second set of gourds, I found such sadness. Two full nests were lifeless, including the one with 7. Those poor parents couldn’t keep up with the demand. There were individual birds dead in other nests. We lost a total of 13 young. There were others that looked weak but hopefully will survive in the coming days of better weather. We fared much better than some of the inland colonies where the temperature soared higher and mortalities were far higher as well.
|The gourds were set up at the end of April.|
We can never really predict how a colony will do in a given year. The purple martins rely on human help for their housing, but only nature can truly provide the right conditions and food sources. Erratic and extreme weather, combined with declining insect populations is not a good scenario for survival for this and other species.
We still have the potential for a good year and good numbers in 2021, but we never know what conditions are in our near future. And we certainly do not know what is in store in the next decades.
|About 11 days old.|