Two Breeding Pairs of Purple Martins Nest in the Same Cavity in 2006
Ken Kostka
Purple Martin Preservation Alliance
http://www.purple-martin.org
02/28/07

        Purple Martins never fail to surprise me, and 2006 was no exception. For the first time in 25 years,  I documented two pairs of Purple Martins using the same cavity during the same nesting season in consecutive successful breeding attempts. The first pair raised five young and moved out by July 4th. The second pair then moved into the same compartment and laid their first egg on July 9th. They raised 3 young that did not fledge until late August. The first pair of martins was banded, so it was definitely not a case of doublebroodedness. Appropriately, this event occurred in compartment #1 of a 28 compartment colony consisting of two wooden T-14's at the Saxon Golf Course in Sarver, PA - a thriving colony that has achieved 100% occupancy for the last several years.

    Several factors probably contributed to this unusual event. First, the early-breeding pair was also the oldest and earliest-nesting pair in the colony. The male was "yellow 096 right ASY-M" which means he had a yellow color band bearing the alpha-numeric M096 on his right leg and he was an "After Second Year" male (2 or more yrs. old). I had banded him as a nestling at the the Moraine State Park colony site in Portersville, PA in the year 2001. He was now five years old, and was the first returning martin to the Saxonburg colony in 2006. The female was also an "old-timer".  She was "blue 132M right ASY-F".  She was banded as a nestling in 2001 at the colony of Robert Yoder of Sugarcreek, OH in 2001, making her 5 years old. Both martins had been residents at the colony for several years. They laid their first egg seven days earlier than any other pair in 2006.
    The second contributing factor was that this pair resided at a colony that was well-trained to accept supplemental feedings during periods of poor weather. Originally taught to catch large crickets thrown into the air during a period of extended, martin-killing foul weather in 2000 (even before these martins were born), this colony had graduated to eating large chunks of scrambled egg placed on a stationary feeder between the two houses. This training proved life-saving in May of 2006 during a nine-day stretch of continuously poor weather that lasted from May 15-23. Dozens of scrambled eggs were consumed, and it is likely that if it had not been for the supplemental feeding, this pair would have delayed incubation to conserve energy, thus delaying their nesting attempt, and preventing the second pair from nesting.
    The third and final factor may have been my attempt to encourage several pairs to disperse and breed elsewhere. On June 9th, I closed 7 compartments, all of which had been claimed (but none of which had eggs), forcing 7 pairs of breeding martins to look elsewhere for nesting cavities. I did not have time to trap and band these individuals before excluding them from their compartments, so it is possible that when I reopened the compartments on June 30th (three weeks later), some of the same martins were still present and resumed nesting. It is also possible that they were martins excluded from other colonies within a 50 mile radius.

 Here is a summary of the information for both the early and late nesting pairs that bred in compartment #1 at the Saxon Golf Course colony in 2006:

First Nesting Pair:         ASY-M: 5 years old. First spotted 4/4/06, banded - YELLOW M096
                                    ASY-F: 5 years old. First spotted 4/13/06, banded - BLUE 132M right, ASY-F
                                    The pair was first spotted together on 4/29/06, sitting together on the porch of Compartment #1.
                                    Laid the first of 6 eggs on 5/6/06
                                    Hatched 5 eggs beginning on 5/26/06
                                    Began fledging 5 nestlings on 6/23/06.

Second Nesting Pair:    SY-M: 1 year old, unbanded
                                    SY-F: 1 year old, unbanded
                                    Laid the first of 5 eggs on 7/9/06
                                    Hatched 4 eggs beginning on 7/28/06
                                    Began fledging 3 nestlings on 8/25/06

The CID's (Clutch Initiation Dates) of these two pairs were exactly 63 days apart.

    To make things even more interesting, there was a second very late-nesting pair that laid their first egg in compartment #20 (an unoccupied cavity) on July 9th - the very same day that the late nesting pair in compartment #1 did. This other late-nesting pair also fledged nestlings successfully. The presence of another late-nesting pair probably helped the martins stay "on-task" late in the season when most other pairs had finished breeding and the colony was largely deserted. The female of the pair that nested late in WH-20 was Yellow A587 left SY-F, who was banded at the Shelocta, PA colony as a nestling in 2005.