Forced Dispersal as a Method of Establishing New Purple Martin Colonies
Ken Kostka
Purple Martin Preservation Alliance
Pittsburgh, PA
http://www.purple-martin.org

            During the 2005 season, the Purple Martin Preservation Alliance (PMPA) carried out a project designed to establish new Purple Martin colonies in southwestern PA.  The strategy was straightforward: close compartments at established colonies and force the martins to disperse to housing at unestablished sites - hopefully to sites where we had been attempting to start colonies for several years.  The idea was originally put forth by Dr. Eugene Morton, a martin researcher with the Smithsonian Institute, who had tried unsuccessfully for many years to establish a martin colony in Northwestern PA. He believed that his lack of success was due to the few large colonies in his area acting as black holes and “pulling in” virtually all of the cavity-hunting martins each spring. Purple Martins prefer, above all else, the presence of other breeding martins when seeking out a nest site and will usually attempt to "squeeze into" an existing colony rather than nest alone at a new site.

              We were able to include six large colonies in the project.  This may seem like a small number, but colonies in Southwestern PA are relatively scarce.  There were only two known colonies in Allegheny County, one in Westmoreland, one in Armstrong, and one in southern Butler Co.  Colonies are more numerous in northern Butler Co.  The PMPA has been trying to establish colonies since 1999 at a variety of sites while at the same time managing the existing colonies for maximum breeding success.  Still, we were unable to establish any new sites in the past five years, and we felt the need to employ an additional strategy. We made some interesting discoveries about the behavior of displaced martins.  The project generated a great deal of enthusiasm among some "would-be landlords" who had tried for years to start colonies, and who saw a huge increase in the amount of martin activity at their sites.

             A total of about 50 pairs of martins out of a combined total of 225 pairs (22.6%) were forced to seek out new housing.  (See table below) Any unused compartments at these sites were also closed to prevent martins from simply moving to a new compartment. The number of pairs displaced at the Zeglin and Youghiogheny colonies is estimated, because the site manager (Jeff Hunt) closed the compartments prior to the martin’s spring arrival. For example, there were 25 and 30 breeding pairs respectively at these two sites in 2004, so he assumed there would be about that many pairs in 2005. Jeff closed all but 20 of the compartments at the Zeglin site, and all but 20 of the compartments at the Youghiogheny site prior to the 2005 arrival. (The compartments left open were the same ones used in 2004) Therefore, it is assumed that 5 and 10 pairs respectively were displaced. At the other four sites, the martins were displaced after they had begun nest-building, but before they laid eggs.

Displacement Table:

Colony Site                                                       Total pairs     Pairs displaced        

Zeglin Dairy Farm, Westmoreland Co.                  *25                 *5
Youghiogheny Country Club, Allegheny Co.          *30                 *10 
Gastown Racetrack, Armstrong Co.                       53                  13
Saxon Golf Course, S. Butler Co.                          28                  8
Moraine State Park, N. Butler Co.                        40                  10
Duke Snyder residence, N. Butler Co.,                  49                  5



            This map shows the results of the project in the area of colonies listed in the Displacement table.  The established colonies have blue description tags; the sites with new activity have white description tags.


     THE SAXON GOLF COURSE DISPLACEMENT:  At only one of the colonies, the Saxon Golf Course colony site near Saxonburg, PA, was I able to trap and band the martins prior to the closing of their compartments.  The bands allowed me to identify individual martins and determine with certainty whether the displaced martins were responsible for the establishment of a new site.  This colony consists of two T-14's that both had 100% occupancy in 2004 and 2005. I used T-14 insert traps to attempt to capture every one of the sixteen individuals I would eventually displace. I was able to capture and band 12 of the 16 martins. Some defied capture.  In several cases, I caught the male multiple times but not the female. Luckily, at least one banded martin from each pair was banded. Each banded bird had a yellow color band with an alpha-numeric code consisting of a letter followed by three numbers, for example "K123".  These bands could be read with a high-power spotting scope while the bird is perched, without having to capture it. I closed the eight compartments on June 8th and June 9th. (See table below) These were the only eight compartments where eggs had not yet been laid. Most of these pairs were subadults, but there were several adult males and even one adult female. Incidentally, displacing these pairs was a difficult decision, not taken lightly. I had invested a great deal of time and money in this colony since I took over management in 2002. In 2001, it was a dwindling 8-10 pair colony in an old unmanageable wooden house. In 2004, it was a thriving 28 pair colony; almost all individuals had been trained to take supplemental feedings.

Listed are the location, sex, age, and banded status of the eight pairs that were displaced from Saxon Golf Course:

WH-4    banded SY-M yellow K404        unbanded SY-F                     compartment closed 6/9/05
WH-5    banded ASY-M yellow K256      banded SY-F yellow K480      compartment closed 6/9/05
WH-9    banded SY-M yellow P538        banded SY-F yellow K448      compartment closed 6/8/05
WH-15  unbanded ASY-M                     banded SY-F yellow K477      compartment closed 6/9/05 
WH-16  banded SY-M yellow K370        banded SY-F yellow K360      compartment closed 6/8/05 
WH-17  banded ASY-M yellow K279      unbanded ASY-F                   compartment closed 6/9/05
WH-23  banded SY-M yellow K414        banded SY-F yellow K479      compartment closed 6/8/05
WH-26  banded ASY-M yellow K216      unbanded SY-F                     compartment closed 6/9/05   

      One of the great unknowns with regard to the displacement of these eight pairs of martins was whether their pair-bonds would remain intact when their compartment was closed and they were forced to disperse.  One reason for waiting until the martins had pair-bonded and begun nesting, as opposed to blocking the compartments prior to their arrival, was the hope that this "delayed displacement" would result in many cavity-hunting pairs that were eager to begin renesting at the closest available site, due to the lateness of the season. I felt that if compartments had been closed early in the season, prior to their arrival, unmated individuals would tend to wander further from the project area and join already established colonies.

    On June 13th, five days after the compartments at Saxon Golf Course were closed, I received a call from a friend who had been attempting to start a colony for several years. He had spotted one of the 16 Saxon martins! Yellow K479 SY-F was seen investigating his site near Portersville, 27.0 miles away! Furthermore, she was with a new SY-M. Apparently her pair-bond with K414 SY-M had dissolved after the compartment had been blocked.  Perhaps the closure amounted to a failed nesting attempt in her eyes. In any case, she did not stay and re-nest at this new site.  She was spotted again several times beginning on 7/17/05 at the Lock 4, Natrona site,  8.7 miles SSE of the Saxon Golf Course site, over 36 miles from the Portersville site. It is also apparent, based on the timing and frequency of these sightings, that she did not breed in the 2005 season. 


   
    The next sighting of a displaced Saxon bird occurred two days later. While reading bands at a colony near the Duke Snyder colony in Butler, PA, I spotted yellow K279 ASY-M.  He seemed to be alone.  I saw him again the next day at the Duke Snyder colony about 1/4 mile away, and again at Lock 4, Natrona on 6/20/05. He was spotted at the Lock 4 site many times thereafter, as well as back at the Saxon Golf Course site on multiple occasions. On all of these occasions, he seemed to be alone. Again, based on the frequency and timing of the sightings, he clearly did not breed. Interestingly, he and his ASY-F mate were the last pair to leave the Saxon colony. They were seen together on the porch of their compartment on 6/13/05, four days after it was closed. Eventually, however, their pair bond  dissolved.

    When over a week had passed without any of the displaced pairs having settled into new sites, I was beginning to become discouraged. The pair bonds had dissolved in at least 4 of the 8 pairs. In addition to the two pairs already mentioned (those containing K479 and K279), I was able to determine that two other pairs had broken up. Yellow K216 ASY-M was still at the Saxon site, but his SY-F mate was  gone. And yellow K448 SY-F was now nesting in a compartment where an unbanded SY-F had died. She was now mated with an ASY-M and had abandoned her SY-M mate.  For a while, I was concerned that the displaced and single ASY-M's that remained at the colony would interfere with the breeding of the existing pairs, but apparently they did not, as 19 of the remaining 20 pairs bred successfully.

    Then on June 17th, when the outlook for new nesting attempts appeared bleak, I visited the Lock 4 Natrona site along the Allegheny River and immediately spotted martins. There were 6 Purple Martins present: one unbanded ASY-M, two unbanded SY-F, two unbanded SY-M, and one banded SY-M: yellow K404, who had been displaced from Saxon Golf Course eight days earlier. I was exhuberant, having attempted to attract martins to this location for over five years! After consulting with the lock staff, I learned that the martins had been present for several days.  K404 and one of the SY-F were carrying nesting material into two of the T-14's compartments. When I later checked the house, I found quite a few green leaves in two adjacent compartments. Eventually, they built a nest, laid eggs, hatched them, and fledged all four nestlings.  There were many visitors to the site, many of which were from Saxon Golf Course. I chronicle the entire 2005 breeding season of this pair, with its many interesting twists and turns, in an article titled  Purple Martins Breed in Natrona, PA as a Result of Forced Dispersal Project.  While I have no proof since she was unbanded, I believe that the SY-F of this pair was K404's mate at Saxon Golf Course, and that they arrived at this site together, their pair-bond having endured.

    THE MORAINE STATE PARK AREA DISPLACEMENT: Three days prior to closing the compartments at Saxon Golf Course, I closed 10 active compartments at the Moraine State Park colony, on June 6, 2005. It was the result of this displacement that provided much encouragement. The day after displacing these 10 pairs, I contacted a friend, Bob, who lives about three miles from the Moraine colony. He had been trying to start a colony for about four years. When I informed him that he should be on the lookout for martins since I had closed 10 active compartments at a site only 3 miles from his home the previous day, he immediately informed me that five martins had been at his site that very morning - June 7th, 2005. He was surprised because he had not had any visitors for about a week and was quickly beginning to give up hope for the season. These five investigating martins consisted of one ASY-M, 2 females (age undetermined), and 2 SY-M's. He said it was very unusual for him to have this many visitors - especially ASY-M's and multiple females - this late in the season. None stayed the night, but two days later, on June 9, 2005, Bob had 8-10 martins flying around his yard in the very early morning. Again none stayed the night, but three martins investigated his housing later in the day.  On June 11th, 2005, Bob had two pairs visit his site. On June 12th, he had two groups of three martins and a few stragglers.  On June 13th, two days later, Bob spotted a banded SY-M with yellow K479 SY-F, who had been displaced from the Saxon colony, 27 miles to the southeast. He had visitors again on June 14th. Although none ultimately stayed and nested, Bob had martins at his colony site every day for about 10 days following the closure of the compartments at Moraine State Park, three miles away. Another would-be landlord in the area who lives near Duke Snyder also a huge amount of activity at his site. On June 11th, Marty saw over 25 martins on and around his housing. Again on June 14, he saw over 25 martins. Marty ended up with 3 SY pairs that fledged a total of 11 young! At least 2 pairs nested in a T-14, the same type of housing most martins had been displaced from. There were over a dozen martin colonies with available cavities in the Portersville-Butler area, and many of the displaced pairs could have dispersed to them as well.

THE SOUTH OF PITTSBURGH DISPLACEMENT  As mentioned earlier, Jeff Hunt closed compartments at two major colonies south of Pittsburgh very early in the season, before the martins arrived. By leaving open a significantly smaller number of compartments than there were nesting pairs in 2004, Jeff was confident that he was displacing at least 15 pairs of martins from the two sites. On May 9th, 2005, an ASY-M arrived at an uncolonized site in Slickville, PA, less than 20 miles from both sites.  Interestingly, this ASY-M was already trained to take tossed crickets, suggesting he may have come from one of Jeff's sites, where some of the martins had been trained to take supplemental feedings. By June 14th, he had recruited an SY-F. Unfortunately, after building a nest and laying one egg in a T-14, the female disappeared. Two SY pairs nested successfully at a new site on the back 9 of Butler's Golf Course (about 3/4 mile from the existing site), where Jeff had been attempting to attract martins for the past couple of years. Jeff also had significant activity at two sites where he had been attempting to attract martins for the past three years. At Vandergrift Golf Course near Apollo, PA, 3-5 martins visited regularly for several weeks. At Beaver Run Reservoir, a pair of martins built a nest but did not lay eggs.

RESULTS AND DISCUSSION: Several displaced martins were seen at relatively long distances from their home colony, suggesting that they may wander long distances in search of a new nesting site. K279, initially spotted at the Duke Snyder colony site 16 miles away, was then seen at the Lock 4 site (25 miles from the Snyder site) He was seen at both the Lock 4 site and the Saxon Golf Course site throughout much of the breeding season, indicating that some displaced martins travel frequently between nearby sites. At least 50% of the displaced pairs at the Saxon Golf Course colony site did not remain together after the closure of their compartment. Perhaps the female considered the closed nesting compartment as a case of reproductive failure and dissolved the pair bond. It was confirmed that three of the displaced individuals remained non-breeders for the remainder of the season, suggesting that the displacements either occurred too late in the breeding season or too late in the nesting cycle. Though none of the pairs had laid eggs, most had completed nests prior to being displaced.  If their compartments had been closed soon after they began nestbuilding, perhaps they would have been more likely to remain together in search of a new nest site. It is very interesting to note that the one pair that did appear to remain together and renest at a nearby site (yellow K404 + unbanded SY-F at Lock 4 site) was also the LATEST nesting pair at Saxon Golf Course. If the project is repeated next year, it may be advisable to close compartments earlier in the season, perhaps around May 25th.

    Also of great interest is the fact that martins did not nest in an old unmanageable, round-holed wooden house with smaller compartments only several hundred yards away from the Saxon colony site. Initially, I was afraid that some martins would try to use this house since it was so close-by. Starlings had nested in it earlier in the season, but they seemed to have left by mid June, and I was afraid the displaced Saxon martins would attempt to nest there. They did not. Interestingly, the one Saxon pair that did appear to remain together and renest at a nearby site (yellow K404 + unbanded SY-F at Lock 4 site) nested in a T-14, the same type of house that they had been displaced from. It will be interesting to see if any of the displaced individuals attempt to nest again at the Saxon colony in 2006. While the combined displacements at Saxon Golf Course resulted in the confirmed establishment of only one new breeding attempt at a nearby site, it is important to consider that some of the pairs may have re-nested at unknown sites, either new or established. If the project is repeated next year, it is important to include as many colonies as possible, as far away as possible, so that martins displaced from their home colonies do not simply take up residence at another established colony.  It would seem important to seek some level of cooperation from as many colony managers as possible.  If landlords are not willing to displace martins, they should be encouraged to at least close unused compartments when the displacements commence.