Part 1: Climate Change and the birds of northern New Mexico
By Robert Dryja
We have been exploring the data of the Christmas Bird Count. Los Alamos now has a snapshot of birds seen in December 2015 (See here.)
The Christmas Bird Count shows that a few bird species are commonly seen while other species are increasingly rare. Ten species of birds account for about two-thirds of all the birds seen in the Los Alamos area.
The other seventy one species compose the remaining one-third of the birds seen. CHART I show this pattern for the 81 species.
Five other areas of northern New Mexico have bird counts going back to the 1950’s. Two hundred sixty two (262) species have been seen over the years among all six areas. At one end of the spectrum a few species are common both in their numbers and the variety of habitats in which they live.
TABLE 1 shows for example that 44 species have been seen in all six areas even though the elevation changes from 5,600 to 8,400 feet—a difference of half a mile. At the other end of the spectrum some species are unique to a single area. This variety among the species can be used to track what kinds of impact global climate change may have for the northern mountains of New Mexico.
Average temperature often is used as a measure of climate change but it is a tricky concept. Consider the following. Put your hand on a hot stove and your foot in a bucket of icy water. On the average you feel all right. Atmospheric temperature faces the same problem. It was 36 degrees at night and 58 degrees in the afternoon for March 10th in Los Alamos. The average temperature was 47 degrees. A look at the records of the National Weather Service shows that 47 degrees actually occurred for about half an hour in the morning and another half hour in the afternoon. Does an average of 47 degrees mean that much?
One way to cope with this variability is to consider many daily cycles for a very long time. It also helps to consider the daily low or high temperature rather than combining them. Fortunately the National Weather Service has 120 years of temperature data available. Chart 2 is based on calculating that average of low temperatures for the 365 days in a year. This calculation is then repeated for each of the 120 years of data.
CHART 2 shows that the annualized average low temperature has moved back and forth between 30 and 34 degrees, a variation of only four degrees. This does not seem like very much. However, these changes are occurring around the freezing point of water. More observation suggests that the annual average low has moved above freezing starting in about 1980. It also appears to have remained typically below freezing for the years from about 1930 to 1980.
Chart 3 shows two additional kinds of averages. The red Ten Year Average trend line begins to smooth out the ups/downs from one year to another. The temperature now has remained above freezing since about 1985. It also has remained below freezing from about 1925 to 1985. The century trend line smooths the ups/downs even more to create to a single curved line over the 120 years. These two lines together indicate that the average northern mountains climate temperature has been following an upward trend for the past thirty years to remain above freezing.
In Part 2 we will consider what may happen to the bird species that are unique to one area. In Part 3 we will consider what may happen to species that are common to all areas.