Abstract
The 1987 breeding season actually began back in the last weeks of September 1986 when our Derbyans were going through the preliminaries of pair bonding. Derbyans, like the other members of the Psittacula genus, pair bond for only one season at a time. This makes it possible to take full advantage of all the members of a particular species for the purpose of extending the gene pool.
In October of 1986, we set up three pairs of Derbyans in side-by-side aviaries, and numbered #1, #2, and #3. The most experienced pair was housed in the #1 aviary. These birds were wild-caught and have been reliably nesting for us the past eight years. The #2 and #3 aviaries each housed a pair consisting of a wild-caught hen (mature, but of unknown age), and a two-year old domestically raised male.
1986 ended like most other years with one exception. Four days after Christmas, we found the male housed in the middle (#2) aviary dead on the ground. (A veterinary report revealed he had died of a nasty bacterial infection.) We were extremely disappointed. The #2 hen seemed a bit distressed too, however, she was a lovely mourning widow for only a short time.
The male in the #1 aviary chewed a hole through the plywood wall that separated the #1 and #2 flights. He slipped through the opening and began to feed and mate with the lonely hen in the center flight! The #1 male continued to go back and forth through the hole in the plywood several times each day. He was feeding, displaying and mating with his hen in the first flight and also with this merry widow in #2. We dubbed the number two hen "Merry".
About ten days later, another hole appeared on the opposite wall of the center aviary. The young male from the #3 flight poked his head through and flew up to the perch to feed Merry! She was, indeed, a busy lady. When he had finished mating with her, he would dutifully return to his own hen in aviary #3.
The pair in #3 was the first to lay eggs, and were only ahead of the #1 pair by a few days. Each pair laid eggs during the month of March.
Two and three times a day we'd observe the #1 male and the #3 male in the center aviary at the same time with Merry. But a menage a trois was not to be. The elder Derbyan male established his dominance, badgering the young male until he scrambled back through the hole and into his proper place in #3 aviary.
On 12 occasions, we discovered the #3 male in the #1 flight! When the #1 male returned "home", he'd drive the younger one off again. The #1 Derbyan male was willing to share his mistress, but certainly not his wife!
Two weeks passed when our Merry disappeared into the nest box and laid her first egg. She laid three altogether, and my husband and I wondered if this little lady's eggs were going to be fertile. Even more important, what if they were? Provided the eggs hatched, how was Merry going to feed those babies by herself?
Normally, it's the male's responsibility to feed the hen while she gets the job of sitting on the eggs for 28 to 30 days. Perching at the entrance hole of the nest box, the male will feed the hen throughout the incubation period. He continues to feed her even after the eggs hatch. It's six or seven days after the hatch before the male enters the box to help feed the chicks directly. At this point in their development, the chicks are nearly doubling in size and food requirements on a daily basis.
Would it really be possible for this one hen to take on the task of raising and feeding those babies? If so, how many days would she be able to keep up with the increasing food demands of the chicks? Would she instead starve, waiting for a male to show up to help feed? The more likely outcome would be that Merry would attempt feeding the chicks by herself for a day, maybe two. We were not optimistic about the survival chances for her chicks in this case. There have been occasions when a single bird has been able to take care of its offspring for a surprising period of time. But more often, unable to keep up, the parent bird allows the babies to die (or kills them) within a few days.
What may seem cold-hearted by human standards is good instinct by bird standards. Better to let one clutch die, survive and return next season when things are more favorable for nesting.
Merry would probably follow her instincts, choosing life for herself and sacrificing the chicks. We hoped she would at least feed the babies long enough to give them a good start before we had to pull them in.
The best option would have been to foster the babies under another pair. However, the other two pairs of Derbyans were on three fertile eggs each by this time. We didn't feel it prudent to try our luck with an experiment to see if Derbyans would tolerate one or two extra eggs in their nest.