A tale of two migrants
September 18, 2013 —
September is here, and many animals in our area are preparing in some way for the onset of colder weather to come. Some insects and many birds have already started to migrate to warmer climes, and it is this migration behavior that enables researchers to get a “snapshot” of the wellbeing of a particular species and its habitat.
By now, broad-winged hawk migration is near its peak in our region. Many counting locations along ridges show daily counts in the thousands around the middle of September as they make a mass movement south. To show how this species is doing in this year’s count compared to last year, I took a 10-day window (September 1 through September 10) from the count site at Scott’s Mountain, located in Harmony Township, NJ, where they have had good personnel coverage and records for the two years for this species. The broad-winged hawk count here for this 10-day period in 2013 was 360 vs. 320 broad-winged hawks in 2012. There is no great variation in the count between 2012 and 2013, especially since this is only a 10-day window.
Our second migrant species (a non-raptor) raises much concern, and many people have noticed the scarcity of monarch butterflies over the summer. Here is the count data for the same site and time window for this species:
Scott’s Mountain Monarch butterfly
2012 count, 557 2013 count, 8
Counts from other sites during the same time frame show similarity to the above count. According to Chip Taylor, director of Monarch Watch (www.monarchwatch.org), much of the decline is due to habitat loss in both the U.S. and Mexico, along with the record-breaking heat earlier this year in much of the country when the monarchs arrived during spring. Taylor stated that with further population decline comes the possibility of the species as a whole being put in peril if another weather or similar event occurs. As he said in an interview for a New York Times article in March 2013, “This is one of the world’s great migrations; it would be a shame to lose it.”