The Purple Martin gathering is once again underway in all its grand glory at their roost on the campus of the Nebraska Medical Center. Each day since later June both this season and last year, a variable number of this particular bird congregates and spends the night in a few trees at the scene. This routine continues for many weeks, and since the roost was first discovered on August 23, 2008, there have been regular estimates made of the number of martins present.
Counts are not available for every evening, but from late-June in 2009, until the birds were gone in early September, there is sufficient information to derive a total of the bird use days. A bird-use day is considered to be the use of the roost site for one night by one bird. So if there are 5000 martins present, this would equal 5000 uses of the roost, or one bird use value. Where an actual count was not made, an interpolated value was imposed, based on an interpretation based upon known counts on days before and after the particular date being considered.
Economic Value of Roost for Martins
In 2009, the Purple Martins were first noted at the roost on June 29th, when there were about 600 present. They were undoubtedly present prior to this, based on their occurrence three days earlier in 2010. Therefore the first date considered is June 28th, and the final date - when five martins were present - was September 13th. This is a period of occurrence of 81 days, with survey details available for 41 of these days.
Numbers were highly variable during the entire season, but somewhat consistent when a span of a few days is considered, with the greatest count of ca. 40,000 indicating how important the roost site is during the birds' migration.
Overall, there were about 736,505 martin use days at the midtown roost.
This number of use days equates to some economic value. The dollar figure used for this evaluation is $5 per day, which is a completely arbitrary amount, but much less than what any one person would expend for a bed for a night. This figure is used to present a minimal though extensive valuation.
The number of bird-use days - for just one species when two others also occur in large numbers - multiplied by a basic, low minimum equates to a value of $3,682, 525. Doing additional math, using a greater valuation, and perhaps considering additional factors would only increase this amount.
This economic valuation does not consider any human-based economic value. If the value of the experience based upon the consistent occurrence of people at the roost site was included, there would be a much greater value associated with the martin gathering. Each and every person whom watches the martins on any particular evening, obviously considers the experience to be worth them taking the time to get to the site, and spend some time watching what is a "free show" by the birds. This valuation is at least equal to the price of going to a movie!
If there is a crowd of 75 present for an hour on a Sunday evening, as recently happened in 2010, it is very likely that a value of $10 could be attributed for each of them, or perhaps just $5 to correlate with the valuation for each bird. However, though no one spent a dime to watch the martins, the night's outing can easily get a valuation of some amount, which would add to the overall monetary importance provided by the birds.
Thus, there would be additional value added to that indicated by the bird use day calculation.
The economic value of the Nebraska Medical Center roost for birds and their watchers is at least $5 million per year.
It should be noted that the only dollars expended for this roost was in 2009, when the Nebraska Medical Center paid to have decals placed on windows of the walkway where bird strikes were occurring. This was done to address the bird mortality which was occurring, for which the Nebraska Medical Center is responsible through the taking clause of the Migratory Bird Treaty Act.
Nothing has been expended just for the birds, and there have not been any expenditures to assist the martins, or to ensure that the roost here, or perhaps somewhere in the future will be present for the benefit of the species which eats so many bugs.
The bug-eating value of the martins is a wholly separate situation, yet which has been evaluated for its importance in the region, and is not readily appreciated.
Martins at the Roost
The figures below indicate the dates considered, the number of martins counted, or an interpolated value when an actual count was not done.
The economic value of these birds is readily apparent, yet wholly unrealized and not given any particular importance. The Purple Martins which gather do not get a single red cent for their being present. The entire gathering is part of their yearly cycle without any regard for any remuneration.
Once the 2010 season is completed, it will provides dates and numbers that will make for an interesting comparison to the 2009 and 2008 details, showing the variability in numbers present on different dates during each season. Having a third year of records will be a very important addition to the survey details for the roost, and allow a much better evaluation of economic value of the roost to birds and bird enthusiasts.