Northern Prairie Wildlife Research Center
In North Dakota, 148 of the 161 breeding bird species observed in the three years are migratory (86 short-distance and 62 long-distance). Not surprisingly, given our winters, only a handful of species (13) are considered permanent residents in North Dakota.
Many species of long-distance migrants (often called Neotropical migrants) have declined in number in recent years. The species receiving the most attention are forest birds, especially those in the East and Northeast.
In North Dakota, however, we found that long-distance migrants had increased slightly in number from 3,634 pairs observed in 1967 to 4,338 pairs in 1992 and 3,956 pairs in 1993. Short-distance migrants, on the other hand, declined from 1967 to 1992, but rebounded in 1993. This group includes ducks and many other waterbirds, which responded positively to improved wetland conditions in 1993. Permanent residents increased steadily through the three survey periods.
Long-term comparisons of bird populations over such a large area are rare, and they provide a better understanding of changes that have occurred in our state. In 1967 and today, North Dakota stands almost alone in having estimates of breeding bird populations for an entire state.
We have used the results to compare bird populations in cropland to those in fields enrolled in the Conservation Reserve Program. Because of a similar study in CRP fields in 1992 and 1993, we could make a valid comparison, and not worry about year-to-year differences in overall bird abundance. That study clearly demonstrates the enormous value of CRP habitat to a number of species, such as sedge wren, grasshopper sparrow, savannah sparrow, and lark bunting. In the near future, we intend to compare aerial photography from the 1960s to that from the 1990s, to relate changes in bird numbers to changes in habitats over that 25-year period.
Surveys such as ours complement more widespread programs, such as the North American Breeding Bird Survey. The BBS uses volunteers, who count birds each year along specified roadside routes throughout the U.S. and Canada. Forty-six of the 3,700 routes in North America are in North Dakota. The BBS is useful for determining long-term trends in bird populations, but it does not relate population changes to habitat features, and BBS results are not very applicable to specific areas such as states.
Perhaps as the year 2017 approaches, our successors will plan another repeat of the survey. It would befit the legacy of the foresight shown by Bob Stewart and Hal Kantrud.