Dove Baby Parents and the Sunday Night Massacre

Behavioral observations of Eurasian collared doves

Posted Oct 11, 2018

For the past two years, our human family has been joined by a Eurasian collared dove family that nest behind the basketball goal in our driveway. It has been a great experience as our human kids have peeked into the nest at eggs and babies when the nest is left open, can see into the nest from an upstairs window, and get to greet the parent sitting on the nest every day as we leave and return home. These dove broods have been part of our family for two years and have allowed us to teach excellent lessons on respect for wildlife, wildlife habitat, and wildlife behavior. My observations of the behaviors are placed in context of evolutionary psychology.   

Near the end of the summer of 2017, a pair of Eurasian collared doves built a nest on the basketball goal in our driveway. It was a fun curiosity, though I did not know of the commitment I had made to them when I allowed them to continue building it. A male and female arrived together, with the female laying two eggs and the pair taking turns sitting on the nest while one kept watch (always visible if you looked for the other parent) and the other got food. Soon the nest had two very ugly dove babies, and the parents took turns bringing them food and keeping them safe. All four were very skittish of humans, and the parents would fly away any time we opened the garage door, drove by, walked by, or fired up the lawn mower. Eventually, the babies got the courage to fly out of the nest and would hunker down wherever they ended up, appearing to regret their decision to leave the nest.

After a day or two of this, they were able to fly, returned to the nest once, and flew off. For a few days, the parents and kids could be seen high on the rooftops nearby, moving around as a family with the parents chasing other birds away and retrieving any of the children who flew off too far. The parents worked as a team to take care of the kids. When they all left, we were sad but happy to be able to play basketball again. It was a wonderful experience! Clearly, doves have a series of behaviors that work for their species. It is a monogamous, pair-bonded species that always lays two eggs and has a mother and father that work together to give the brood the best chance of successful development.  They maximize their individual reproductive fitness by working together.

In the early spring of 2018, the nest was rebuilt. I mentioned this to my father, a field biologist, and he explained that Eurasian collared doves are a monogamous, pair-bonded species who will re-nest in the same location year to year. I thought “Cool, we get another nest this year and they will be gone in a month.” So the same thing happened as before, with all of the same behaviors except that the doves were no longer afraid of us. Then in late spring, mom showed up and dropped two more eggs in the nest, sentencing us to another basketball-free month. No problem, we’ve got this. One more round.

In the summer of 2018, mom showed up again and dropped her third brood (two eggs) of 2018 (fourth overall). But this time, dad wasn’t around. He never came back. My guess is that he was eaten by a cat or some other predator. This was a much more sad set of events to watch. The mom sat on the eggs but could not get food for herself and keep the eggs warm at the same time. She did her best, but spent so much time off of the nest that only one egg ended up hatching. She left the nest unguarded while she got food for herself and her baby, in contrast to the protection the babies had received with two parents. Moved by the situation, my wife suggested that we step in and take turns with the mom to get food for the baby, but I dodged that one by suggesting that it was likely a federal crime to interfere with a migratory bird. My wife was unconvinced, but I cited the Migratory Bird Treaty Act of 1918, even though I don’t think that is exactly what the Treaty said. It worked, and I got to continue as an observer and not a surrogate bird mom.

The baby, lacking the stimulation of the other baby, did not behave the same as the previous broods. In the previous broods, the babies had been attentive and alert, spending most of their time oriented in opposite directions from each other (rump to face) and turning around to look at each other frequently. This lone baby had no such stimulation and was much more fascinated whenever I walked by, as it was the only movement it saw other than its mother. This baby eventually left the nest and when that happened, mom and baby bravely faced the world together, never leaving each other’s side once the baby was capable of flight. Then they left and I thought I would get my basketball goal back.

But mom showed up again, unaccompanied by a male, and dropped two more eggs for her fourth brood of 2018. Obviously, she had managed to find a male who was willing to inseminate her but not commit to a pair-bond. This time, both eggs survived and she raised the family herself, without the help of a partner. One Friday evening I came home from work and checked on my bird family before checking on my human family. One of the babies had left the nest, which is always an exciting moment to find has occurred! But I noticed that the mom had to chase the baby around to protect it and leave the other baby unguarded. For two years and three broods with a partner, the male partner had fulfilled the role of splitting protective and nurturing duties with the mother, where one parent would stay with each baby if they split up. This was no longer an option for her and was now a problem as the two babies had behaviorally developed at slightly different rates. Solving this problem, the mom was with a new male partner on Sunday evening. Mom, step dad, and baby were all on the roof watching over the other baby who looked about ready to jump out of the nest at any minute. They were not yet splitting parenting duties, but I was confident they were on the right track to surviving as a family as they stood together on the roof watching the sunset.

Sadly, Monday morning I awoke to find feathers all over the grass not far from the nest.  Most likely, the baby had flown just over our fence from our front driveway to our backyard, either late in the evening or after dark. Perhaps a hawk found the baby before it got dark (maybe even plucked it from the nest), or perhaps a cat found the baby on the ground. Maybe an owl got the baby. Either way, there was a pile of feathers in the morning, no bird in the nest, and the rest of the dove family skipped town, not to be seen again so far, leaving behind a sad, empty nest.

These behaviors make sense from the perspective of evolutionary psychology. A monogamous, pair-bonded species allows each of the two parents to invest appropriately in the care of their offspring. As the mother has more invested in the brood (i.e., time spent pregnant), it is not surprising that the mother was the constant in care for all of these broods (Apostolou, 2014; Mather & Hurst, 2014; Trivers, 1972). Since children invoke costs to parents (Mock, 2011), such parental coordination behaviors maximize reproductive value (Surbey, 1998) for individuals in that species. In the first fatherless brood, only one egg hatched and the mom did not seek another mate. However, in the second fatherless brood, both eggs hatched and she found a partner just as the first one left the nest and the second one did not. That is, she found a partner exactly at the time when the developmental discrepancy manifested and her reproductive fitness was in the most jeopardy. She likely found a young male to step in who had yet to find a long-term mate.

Additionally, survival maximizing learning also occurred. The behavior of “nest at the same location as long as it is successful, abandon if something goes wrong” is an adaptive behavior in ensuring the safety of the nest and maximizing the chance of increasing reproductive value.

Thus, in a monogamous, pair-bonded species, two parents are better than one for Eurasian collared doves, who always lay two eggs and attempt to raise two babies.

References

Apostolou, M. (2014). Sexual selection under parental choice: The evolution of human mating behavior. New York: Psychology Press.

Mather, R. D., & Hurst, A. C. (2014). Looking up from the bottom of the family tree. [Review of Sexual selection under parental choice: The evolution of human mating behavior.]. PsycCritiques, 5(19).

Mock, D. W. (2011). The evolution of relationships in nonhuman families. In C. Salmon & T. K. Shackelford (Eds.) The Oxford handbook of evolutionary family psychology (pp. 51-62). New York: Oxford.

Surbey, M. K. (1998). Developmental psychology and modern Darwinism. In C. Crawford and D. L. Krebs (Eds.) Handbook of evolutionary psychology: Ideas, issues, and applications (pp. 369-403). Mahwah, NJ: Lawrence Erlbaum.

Trivers, R. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man: 1871- 1971 (pp. 136-179). New York, NY: Oxford University Press.