In this ‘Behind the Paper’ blog post, we’re getting real about parenthood! From their recently published paper: “Mate desertion affects offspring survival, development and physiology in a songbird with multiple parental strategies“, author Valentina Alaasam explains the “hidden cost” of abandonment of rock sparrow offspring. In their research, Alaasam and team sought to understand the diversity of avian parental care by exploring rearing periods and the physiological stress placed on chicks due to having only one arm of parental care. Their findings paint a picture of single parenting in the avian world. When she’s not out and about studying birds (and salamanders!), Valentina rock climbs, skis and enjoys all the outdoors has to offer. Valentina reminds us of an important mindset to have in academia: don’t be afraid to fail!
Family life in the animal world, much like in humans, is not always peaceful. Raising offspring demands time, energy, and cooperation — and sometimes, parents don’t fully agree on how much each should contribute. Each parent would benefit by investing a little less and leaving more of the work to their partner. This tension, known as sexual conflict, helps explain why parental care varies so widely across species. In some animals, both parents share the work; in others, only one parent (most often the female) stays to care for the young while the other leaves.
Our research set out to understand this diversity from a different angle: what happens to the offspring when one parent leaves? Do the young pay a price for being raised by a single parent? We studied what occurs after male parents abandon their broods in a bird species, the rock sparrow (Petronia petronia), where the offspring rearing period is rather short and lasts for about 20 days. We found that the remaining females could not, on average, fully compensate for the loss of their partner’s help. As a result, nestlings had lower chances of survival and showed signs of physiological stress in early development. Specifically, we found higher levels of corticosterone and oxidative stress in chicks raised by a single parent.
Our findings reveal a hidden cost of parental abandonment that goes beyond growth and survival. Conflict within the family — just like harsh environmental conditions — can induce physiological stress in the young that survive. In other words, the social environment at home can be just as stressful as the natural environment outside.
For this research, we were fortunate to work with a population of rock sparrows breeding within the Sierra de Guadarrama National Park, located just an hour from Madrid in central Spain. This study was made possible thanks to the long-term monitoring led by our Spanish collaborator, Alejandro Cantarero, and through an international collaboration between the Complutense University of Madrid (Spain), the University of Padova (Italy), and the University of Nevada, Reno (United States).
Fieldwork is one of the most rewarding aspects of our research. We collected a combination of behavioral data using video recordings at the nests, and morphological and physiological data from both parents and nestlings. These data allow us to investigate the causes and consequences of mate and offspring desertion.
At the start of this project, we were skeptical that parental desertion could have measurable effects on offspring physiology given the relatively short time between sampling periods (day 8 and 14 of development). However, our results revealed strong effects of mate desertion on both offspring survival and physiology, demonstrating that the absence of care from one parent can significantly challenge nestling development.
The next key question arising from this work was why some males desert their nests in the first place. If desertion so clearly compromises offspring survival, what do males gain by leaving? We are currently testing several hypotheses, including low paternity, opportunities for re-mating, and potential for re-nesting, to better understand why some males act as devoted fathers while others do not. Another aspect of this research we are curious about is how the physiological stress experienced by offspring in early life might affect them later in adulthood. It would be fascinating to recapture some of them in subsequent years and see if there is any effect on survival or reproductive success as adults! These are the kinds of insights that are only possible through long-term monitoring of populations, like the system we have here.
I received my Ph.D. from the University of Nevada in 2022, and I am currently an NSF postdoctoral fellow at the University of Washington. My interest in ecology developed in undergrad, where I had my first field work experience studying hellbender salamanders in Appalachian streams. Because of that experience, I ended up majoring in biology. Though not sure what I would do with a biology degree, I knew I was the happiest when I was out in the streams and holding those amazing animals. I attribute the rest of my career trajectory to some amazing graduate student mentors who encouraged me during that time. My current science obsession (and study focus) are hummingbirds! I hope my postdoctoral research will help us understand how these extremely tiny birds can sustain such a fast-paced life in the face of anthropogenic change.
A major barrier that I experienced was not knowing that being a ‘scientist’ was a career option for me. Growing up, I couldn’t relate to the faces I saw in biology textbooks and didn’t realize there was an active field (especially outside of medicine) that I could participate in. Still today, each time I succeed it feels like a surprise, like I’ve snuck into some club that I am not really supposed to be a part of. I hope that by adding my face to those biology textbooks someday, I can change that for the next generation.
One piece of advice I would give my younger self (or anyone in similar shoes), is to not be afraid of failing. As scientists we actually learn more by failing than we do by succeeding – we learn answers to questions that we didn’t even have the foresight to ask! Failure is an opportunity to reshuffle your perspective and think creatively, and it is often where the most ground-breaking discoveries begin. A second piece of advice is to not take yourself too seriously – prioritize whatever configuration of work-life equilibrium works best for you. Outside of research, my passions include rock climbing, backpacking, skiing, running, biking, crafting, cooking, and (most recently) being a parent!
