05 October 2008

Roost of Purple Martins at Midtown Omaha an Autumn Thrill

The first known occurrence of many thousands of Purple Martins at a readily accessible roost in midtown Omaha was a thrill for many bird enthusiasts of Omaha and Council Bluffs. After the initial public report of the roost and its thousands of the birds, there was a regular crowd each evening to watch the arrival of the birds, and the aerial spectacle of birds flying about in the cerulean skies and then descending quickly into the roost trees.

Indications of Roosting

The first indication of numbers of martins in midtown occurred 10 August, when at least 450 were noted in the Carthage neighborhood near 50th and Cuming Streets. On the next two subsequent days, additional numbers were seen above Dundee, east of 50th Street and Underwood Avenue.

The first thousands were seen in the evening from a vantage point on Izard Street at 44th, in the south Walnut Hill neighborhood. On the 16th the approximate count was 1750 in bunches, moving southward; 740 from ca. 7:45 to 8:25 p.m. on the 19th; and 1700 on the 20th from ca. 7:45 to 8:25 p.m. On the 21st, there were only about 200 in the Walnut Hill vicinity, but about 2000 in the airspace east of the cathedral at 40th and Webster Streets.

With the martins being seen so late in the evening - after checking details of roost details on the internet - there were indications there might be a roost in the local area. One possibility was the many trees at the Joslyn Castle grounds. Although no roosting was occurring there on the evening of the 22nd, large numbers were seen in the airspace to the west.

Scene of the midtown Purple Martin roost at Omaha. The roost is the trees below the skywalk just to the right of the powerline pole, and just above the middle of the picture.

Early in the morning of the 23rd, the search route went southward along Saddle Creek road, and upon getting closer to Dodge Street, more martins were seen, and could be heard at pre-dawn when there was little vehicular traffic and very little city noise. Proceeding onward, about 17,500 were seen - in an approximate count of groups - departing from less than ten ash trees on the southeast corner of 44th and Farnam Streets.

Visits were made each evening to the roost site on subsequent dates, to evaluate the number of birds. The following counts - approximate numbers based on counting groups and by comparisons from night to night - were kept:

08/26/2008 - 17,500: minimum noted expected at martin roost
08/25/2008 - 18,500: approximate number counted, by bunches, from 6:05 to 6:40 a.m.
08/29/2008 - 25,000: group consensus on minimal number
09/02/2008 - 35,000: evening at the roost
09/06/2008 - 8000: into the evening roost
09/07/2008 - 7500: into the evening roost; 20 people watching
09/08/2008 - 10,000: into the evening roost with great zeal
09/10/2008 - 12,500: into the evening roost; ten people watching activity done by 7:50 p.m.
09/12/2008 - 10,000: on a misty, cloudy night; birds arrive and swoop around once or twice and then swoop into a roost tree on these rainy evenings; four people watching
09/13/2008 - 7500: late arriving groups on a clear night; 100 about 7:20 p.m., and finished about 7:55 p.m.; small groups were still arriving after the main bunch was already in the trees.
09/14/2008 - 1100: four watchers at the roost under a clear evening sky.
09/15/2008 - 1100: seven watchers during 7 to 7:45 p.m. interlude.
09/16/2008 - 7500: six watchers, plus other transient viewers; arrived a bit after 7 p.m.; swooping about and not into trees until after 7:30 p.m.; more moving about among the trees than usual; no strikes despite birds swooping over the north skywalk.
09/17/2008 - 1000: action mostly from 7:15 to 7:45 p.m.; nine watchers, including a couple with two pre-schoolers.
09/18/2008 - 1000: four people watching at the evening roost.

The television tower upon which the martins would roost and flit about, prior to their winging into the roost, two blocks eastward, as the martin flies.

09/19/2008 - 1000: first notice that about 100 martins were sitting on KPTM television broadcast tower two blocks to the west, and some others flying about the site before flying over to roost; four people watching.
09/20/2008 - 1000: into roost 7:20 to 7:40 p.m.; ca. 100 first sit and flit about KPTM tower two blocks to the west, and some other flying about the site; three people watching.
09/21/2008 - 500: after swirls and circles of aerial flight, into roost 7:20 to 7:40 p.m. About 100 birds were sitting on the television tower with some others flitting about there. Only two watchers this evening and the rest of the evenings until the martins were gone.
09/22/2008 - 500: after swirls and circles of aerial flight, into roost 7:20 to 7:40 p.m.; ca. 100 first sit and flit about KPTM tower two blocks to the west, and some other flying about the site; three people watching.
09/23/2008 - 500: a few tower sitting at 6:50; finished by 7:30 p.m., since the sunset was earlier.
09/24/2008 - 125: from about 7:10 to 7:30 p.m.
09/25/2008 - 65: flying up high in the aerial realm, then with a quick swoop in, done at 7:30 p.m.
09/26/2008 - 65: flying up high, then with a quick swoop in, done at 7:30 p.m.
09/27/2008 - 5: four then another one; only three seen coming in by the two watchers; done at 7:20 p.m. on a nice evening for watching.

There were no martins at this locale on subsequent dates.

During the entire period, an approximate 150 people watched the birds at the roost. Some of these were people that certainly enjoyed watching these birds, and returned on several occasions. The largest number was on October 7th, when the 20 people were present, including a television reporter. Only two of these people were present every evening once the public became aware of the roost location. There was only one watcher that was there very night after the discovery of the roost location.

Any concerns of campus security were quickly assuaged once they realized why there was a congregation on campus grounds. People had first gathered on the public sidewalk along 44th Street, across from the campus trees where the martins spent the nights. After they had stopped and asked a couple of time why we were standing there on the medical center grounds, they understood the reason on subsequent nights. It wasn't until near the end of the martins gathering, that an a security man stopped again and asked. That was the last time this happened.

A slight advantage of the roost locale was accessibility. There was ample parking right at the spot, and some visitors parked at a lot across the corner to the northwest.

One of the special treats for those that came to enjoy the martins again and again were delicious treats. Twice there was homemade, flaky crust peach pie. And a couple of times, an ample bunch of fresh, home-grown tomatoes to take home were provided by the martin man from Council Bluffs, Dennis Devine. After working with martins for about 35 years, this was his first opportunity to enjoy thousands gathered at a roost. He provided information on purple martins to many of the visitors to the roost site.

Additional Roost Notes

On August 18th, 2007, there was an estimated 2000-4000 martins noted by Justin Rink above the Joslyn Castle grounds on 40th Street. Then two days later, on the evening of August 20th, there were an estimated 12,000-15,000 martins noted by birder Rink, swarming over the Indian Creek Nursery, just four blocks northwest of 44th and Farnam.

These two reports indicate the probability that the martins may have been using the midtown roost site last year as well.

There was a report of an additional, smaller roost at Lake Manawa, in Iowa. This site was checked on 13th September, and a group of at least 500 birds was located in a cottonwood tree on the west side of the lake, by Babs and Loren Padelford.

The Padelfords had first noted roosting martins at the lake in mid-August 1977, when thousands were present. About 6000 were counted on 8 August 1978. There were an approximate 2000 birds at the Lake Manawa Roost on 5 August 1991 and again on the 30th of the same month. Several hundred were counted here in the same time period, in 1994, 1995, and 2003.

This is the only other martin roost in the region where more than 1000 birds have been known to occur.

Bird Strikes

Upon finding the roost on the 23rd, there was also indications of mortality from birds striking the skywalk between the Kiewit Tower and the Clarkson Doctor's Building South. There were four carcasses on the street beneath the skywalk.

It is very likely that additional strikes occurred before the roost was discovered on August 23rd, since the birds had probably been present for a week or two, and that the carcasses had been thrown away by maintenance staff.

This is the tally of known strikes:

8/23: 4
8/25: 5
8/26: 3
8/28: 3

After the few couple of days of seeing the number of strikes, and they were continuing, contact was made with officials of the Nebraska Medical Center to inform them that birds were being killed at a hazardous locale, and suggesting that something should be done. After the skeptical response, information was also provided to an official of the U.S. Fish and Wildlife Service, who also contacted the Medical Center and informed that of aspects of the Migratory Bird Treaty Act, and how this applied to the negative impacts on the martins.

In response, some banners were eventually hung on the inside of the skywalk, on the west side. The preliminary view was that this effort was working, since the strikes stopped.

It is possible that this interlude was a result of birds realizing that the skywalk was a hazard and avoiding it. The strikes seemed to reoccur when the number of birds decreased, but subtle variations in behavior suggested that some new birds had arrived, and were not familiar with the setting, resulting in bird strikes happening again. This was also when it was realized that the banners were not being effective, and seemed to influence what-so-ever on making the glass walkway visible enough for the birds to avoid a collision. Based on numbers of known strikes, there were more after the banners were put in place.

9/04: 5
9/05: 1
9/07: 4, all at the south skywalk
9/08: 8
9/09: 2
9/13: 9, most of these were stunned birds, some which could fly and leave the site in a few moments, although four were held for a time until being released or placed on a branch of a roost tree

By being present at the roost site when the birds arrived and were flying about before alighting into the trees, any birds that did strike the glass of the skywalk could be retrieved and moved away from the concrete of the roadway to allow them to recover, and to make certain there were not run over by a passing vehicle. The roadway has a regular volume of traffic going to and from a parking garage.

The result of more than half of the strikes was a dead martin.

Seven of the strikes occurred at the north end of the south skywalk between the Kiewit Tower and Clarkson Tower. Dates of these events were the 7th, 8th, 9th, and 13th of September. There was no effort to place banners or other items to make this locale less of a hazard to the flying birds.

Although there were a couple of thousands European starlings and many hundreds of common grackles, there were no instances seen where they had struck the glass skywalks.

Looking Ahead

Purple martins are known to continue to use the same roost sites for many years. If the martins would occur again next autumn, the locale should be visited earlier in August to discover when the roosting behavior starts.

To address bird strikes, an effective means of indicating the presence of the skywalks will be necessary. Instead of banners, an option that would work well would be dark-colored window blinds that could be kept open during the day for visibility, and then simply closed to block the view through the glass and make it readily apparent to the martins as they fly about between the towering buildings. This would require only about ten blinds to cover the windows on the west side of the north skywalk, and for the north windows at the south skywalk.

The purple martin roost is a unique spectacle for Omaha, and the local region since there is no other roost of this magnitude known in a multi-state region. The martins need to be truly appreciated and despite what is left behind by the number of birds, when considering the martins, grackles and starlings. The setting needs to be safe, not a hazard where unsuspecting birds are injured or killed. This can be readily accomplished and would be greatly appreciated by the many martin enthusiasts of the river city.

Martinesque skies on a late-September evening at midtown Omaha.

No comments:

Post a Comment