Mother Nature’s boom to bust
Published 9:54 am Wednesday, August 19, 2009
This was looking like a banner year in Austin. The number of nesting pairs of purple martins in housing erected by the Izaak Walton League local chapter had climbed from 12 in 2008 to 22. In all, 114 eggs were laid of which 88 resulted in baby martins. As of the July 14, weekly nest check by Bob Goetz and the 4-H shooting group, optimism for growth in purple martin numbers was running high.
Then came the cool weather later that week and over the weekend. Lows reached the 40s and with highs in the 50s. By the July 21 nest check, the damage became immediately apparent. Five viable eggs and 13 young were all that had survived.
All across the northern tier of states, from Pennsylvania to Minnesota and into Canada, the cold weather had reduced the number of insects flying to the point that the adults could barely survive let alone feed a nestful of hungry babies. Most of the fatalities apparently starved.
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Austin veterinarian Michael Williams examined two of the dead nestlings. His analysis confirmed the suspicion of a massive die-off because of the lack of food, by the emaciated appearance of the babies. One body was sent in to a lab for further examination.
The Austin chapter of the Izaak Walton League is active in issues of the environment, including preservation of clean water, productive soils and natural spaces. The purple martin project was begun the spring of 2006 when three used aluminum housing units were erected by Ikes at East Side Lake’s park and two new ones provided by David Crandall and Double K Specialty owner Kyle Klaehn at the Mill Pond. Another house made of wood was built and erected by Ikes volunteers at East Side Lake last spring.
The purple martin, native to Minnesota, is the largest member of the swallow family. They migrate from their wintering ground in Brazil to Minnesota starting in early April each year. Their diet is exclusively flying insects which may account for their historic popularity for back yard birders. Their cheery song and acrobatic flying add to the enjoyment.
Originally their nesting sites were in hollowed trunks of dead trees. Native Americans wanted their insect eating ability around their home sites, so they hung out gourds that were hollowed out and dried to attract the martins. More than a century of logging and the pruning out of dead trees has resulted in the martin’s almost 100 percent dependency on man provided housing.
According to Bob Goetz, the Ikes purple martin project leader, the number of active housing sites in Austin had dropped from dozens in the 70s to two in 2006 when the project was started. Many previous martin landlords had died moved away or could no longer maintain and clean the houses every year.
Some sites were no longer suitable because of trees growth around them. Other housing had been taken over by English house sparrows and European starlings, both alien imports that have proven to be arch rivals of the native martins for nesting sites. Goetz solicited a number of these used houses from current owners and some of those were able to be rebuilt for the 2006 nesting year. The Ikes have also provided and erected rebuilt and new housing for a number of private property owners, including a unit at The Village Coop.
This year’s nesting season for the purple martin is nearing completion. The last three chicks in one nest at East Side Lake fledged (began flying) about Aug. 15. Soon they will join thousands of others at major roost sites scattered around the states. These are usually wetland areas, but may be only a long bridge which has roosting ledges under it.
From these sites, each day some will begin their flight south, while others are arriving at the roost, all eventually island hopping between Florida to Brazil, or taking the direct route across the Gulf of Mexico, or they will head southwest to Central America and then to Brazil.
Purple martin landlords will now clean all the compartments in the houses and close them up so the sparrows and starlings cannot use them. Then in the spring, at the first chirp of the early arrivals, the houses will go back up and, hopefully, old adults and returning youngsters from this years hatch will again help control the flying insect populations in Austin.