Carolina Wren and House Finch Banding Notes

As a monitoring technique, bird banding has strengths that nicely complement visual or audio surveys. Two basic appeals of banding are to separate known individuals from a group or population and to potentially track such birds over time and distance. Although sample sizes can often be low, the results can be enlightening.

Like cardinals and titmice, Carolina Wrens are a relative newcomer to Michigan. Records before the mid-1950's were sparse, but in the early 1970's, the species began to rapidly increase in numbers. The surge was interrupted by the brutal winters later that decade, but ten years later, the increase renewed. Aside from setbacks in the last few years, the population has continued to rise dramatically. This trend was reflected at the local level. On the Muskegon CBC, the first birds were two found in 1975. The next finally came in 1987 (a singing male seen by myself and other Zone 2 birders by the south shore of Muskegon Lake). Since then, the pace of sightings has accelerated, but the species remains irregular in the county.

In Laketon Township, between 1960 and 1982, Larry Walkinshaw captured three individuals (on 9/27/70, 9/29/70, and 5/29/71). At the Muskegon Lake Nature Preserve, I caught my first Carolina Wren on 9/25/07. That bird did not linger, and for the next few years, I saw or heard no others there. However, in the fall of 2012, one began singing at the preserve on October 25. On November 15, he was joined by a female that promptly flew into one of my nets. Four days later, the male finally also blundered his way into a net.

At the time, I was not sure of the sexes of the captured birds. Males and females are identical in coloration, but the measurements implied different sexes. Skull development definitely indicated that both had hatched that summer. These birds stayed the winter, and they bred this past summer. Hence, these birds had chosen their breeding territory in the fall. Sexes, residency, and breeding status were confirmed when I recaptured both birds in early August. Despite a brood patch on the female, I never heard or saw young birds, so their first reproductive effort may have failed.

Although these birds remained vocal all fall, they were remarkably net-shy. I did not recapture the male until the final day of the banding season, on December 4. Comparing the photos from the 2012 and 2013 captures revealed the subtle distinctions in immature and adult wing patterns. The male is pictured twice above (2012 left, 2013 right).

Another recent arrival to Michigan is the House Finch. Native to the western United States, this species spread westward from an unplanned release in New York. Three birds caught by Walkinshaw in August 1976 were among the first for Michigan. Statewide, the species was first seen on a CBC in 1979. On the Muskegon CBC, it appeared in 1982. By the mid-1980's, House Finches were clearly established in Michigan. Populations peaked by the mid-1990's, but they have since declined and leveled.

Despite its permanent residency status in Michigan, the species is quite migratory, much like Blue Jays. Such movements tend to occur late in the fall (as with juncos, goldfinches, and Tree Sparrows), but they can be substantial in numbers and distance. Both in the spring and fall, numerous flocks pass over the dunes.

Two of my recoveries testify to this dispersal. One banded in 2007 was found the next spring near Bremen, Indiana, 127 miles away; and one from 2011 was found this past summer in Osseo, Wisconsin, 264 miles away (depicted below). Such movements help explain the speed of colonization in Michigan. However, House Finches are not nomadic. A few individuals have been recaptured at the MLNP banding station in subsequent years.

Such dispersal promotes gene flow and species survival, and it occurs to various degrees even among the most "sedentary" birds. An example was a Ruffed Grouse that I first saw at MLNP on October 4 this fall. The preserve seemed like an odd location for this species, especially considering how drastically grouse have declined in Muskegon County in the last few decades. I was glad to see one in the greater Muskegon area after an absence of several years. We will see if this individual remains through the winter.

- Brian Johnson