The first three years of data collection our most populous species was the Dark-eyed Junco, Junco hyemalis. House Sparrows, Passer domesticus, also known as English Sparrows had never been observed at our feeding station. Then during the 1999 – 2000 school year we saw a dramatic drop in the Dark-eyed Junco population and experienced a huge influx of House Sparrows. The effect was impressive enough to catch the attention and concern of nearly all of my students. Why was this happening? Was it a coincidence? Did the construction of houses and the loss of the field behind our school have something to do with this change? Were the House Sparrows driving away the Juncos?
Aerial photo showing the rural landscape around our school in 1996 (left) and the suburban development around the school in 2002 (right). The yellow star marks the approximate location of our bird blind.