This post was contributed by Dominic Janus, lead author of a paper in a recent issue of the The Wilson Journal of Ornithology documenting a European Starling feeding nestlings at a Hairy Woodpecker nest.
European Starlings are an invasive species in North America. They’re known to harass native woodpeckers and take over active woodpecker nests for their own use. So imagine my surprise when I happened to find a Hairy Woodpecker nest with three young in spring of 2020 being fed by a mother woodpecker and a starling! For the mother woodpecker, this was as if a known intruder entered her home, helped feed her family and clean her house until her kids were grown, then disappeared. This bizarre behavioral narrative is not complete without the events that led me to discover it, so I’ll begin there.
At the beginning of 2020, I was temporarily living back at home in Guelph, Southern Ontario, after finishing my undergraduate degree at the University of British Columbia and spending nine months working in fisheries on the magical coast of Western Vancouver Island. I came home to reset, hoping to find some avian field work job in order to better prepare myself for grad school. But as I schemed about how to return to my dream world of studying birds and set a course for a career in science, my plans for work and travel that year were abruptly put to bed by the pandemic.
Others had it worse. I was healthy, close to family, and ready to adapt to the circumstances. You could feel spring migration just around the corner in early April in Southern Ontario, so at least I had something real to look forward to. I’m an avid photographer and keen naturalist, and I’ve learned over the years that curiosity in nature is always rewarded. As much as I wanted a cool bird job, what I needed to do was just to get out there on my own time.
Spring in Southern Ontario means habitats packed full with birds, canopies full of warblers, and a succession of new migrant species appearing with every warmer day. On a Sunday morning in late May, I spent a surreal fifteen minutes perched on a tree over the Speed River watching a Prothonotary Warbler near my favorite trail close to home – a stunningly yellow bird. Upon coming home, I learned that this species had never been reported in my county. I uploaded my sighting to eBird, together with a photo and recording of its song, and received a congratulatory email from an eBird reviewer about the significance of my sighting. Surely, I thought, this may end up being the coolest bird observation I’d ever make.
I returned to the river that afternoon to get another glimpse of the Prothonotary Warbler, as did other birders. It was gone. But before leaving, I investigated a spot where I’d been hearing woodpecker nestlings begging for several days prior but had been unable to locate the nest cavity. This time I managed to find the nest, and after a few minutes I saw was a European Starling popping its head out of the nest hole then flying away carrying something in its beak! The nest turned out to be a Hairy Woodpecker nest. I took photos of the unusual event and added it to my list of the cool things I witnessed that day.
The next morning, I returned to the woodpecker nest and got enough photo and video evidence to confirm that I had found something rare and relatively undocumented in science. The universe had presented me with an opportunity to conduct some interesting research, so I immediately began my pursuit. I got in touch with Dr. Elizabeth Gow at the University of Guelph, an expert on cavity nesting birds and someone I already knew. She checked the nest for herself and shared my fascination with this unusual interaction. We made plans to write up and publish this finding in a short natural history note.
My observation was an example of interspecific feeding (i.e. one species feeding offspring of another). The European Starling, which we identified as an adult male, was feeding woodpecker nestlings and cleaning the nest cavity by removing fecal sacs – “full service childcare,” if you will. Also feeding, but never seen removing fecal sacs, was the mother Hairy Woodpecker. She would occasionally chase the starling but ultimately let it do its thing. Was she aware of the beneficial service being provided by the starling to her offspring, or simply incapable of defending her nest from the larger starling? Once, she even fed her young while the starling was inside the cavity! I took that as a sign that she had just accepted the situation.
Dr. Gow and I identified the absence of a male Hairy Woodpecker as one factor that may have helped trigger this interaction. A defensive male around the nest would have likely been enough to deter the starling, and we suspect the father may have been predated. I remembered seeing a pair of Hairy Woodpeckers in the same area weeks before my observation. We also theorized that warmer-than-average winter temperatures in Southern Ontario may have caused the Hairy Woodpeckers to advance their breeding timing into closer alignment with the earlier-breeding starlings.
Ultimately, we’ll never know the reason behind this starling’s devotion to the young of another species with seemingly no benefit for itself. I initially suspected that the starling was a female who may have attempted to take over the active woodpecker nest and lay her own eggs in the cavity. Starlings are known to do such things (Cabe 2020), so the narrative of a failed attempt to steal the nest that somehow turned into parental care is plausible, but less likely given the starling was a male. The open, begging mouths of nestlings can be enough to stimulate a feeding response from adult birds (Tinbergen 1948), possibly even other species. I like to imagine this as an irresistible force that overcame the starling as it entered the woodpecker nest cavity for the first time during a reconnaissance visit of a hopeful nest hole, but instead ran into three hungry woodpecker babies.
The starling delivered more food than the woodpecker nestlings could handle. It frequently arrived at the nest with a big juicy worm curled up in its beak. The nestlings had a tough time consuming each portion, but like a good parent, the starling was always ready to help. If a worm unraveled during the process of feeding, the starling took it back to a perch and neatly packed it back up in its beak before returning for another attempt.
All three young woodpeckers successfully fledged from the nest. Unfortunately, I wasn’t able to witness their leaps of faith from the nest to the forest floor. In the final two days of feeding before the last nestling fledged, I noticed that the starling would perch just above or below the nest with food for periods of time before feeding, instead of going straight to the hole. Food in mouth, it sat in direct view of the loudly begging nestling, and frequently flew to the hole for only a few seconds before returning to its perch still carrying food. Interestingly, it was almost as if the starling was trying to coerce the nestling to leave the nest! As far as I know, neither the mother woodpecker or the starling fed the young once they fledged; it was time for them to fend for themselves. I really hope all the youngsters made it to adulthood.
There were at least two starlings in the area, but I could only confirm nest visits by one of them. To make the situation even more interesting, one day I noticed a Downy Woodpecker nest about twenty meters away that was also being visited by a starling! Both a male and female Downy Woodpecker were agitatedly vocalizing by their nest as a starling perched within a few meters from their nest, sang, and even inspected their nest hole, but didn’t enter. I could have never predicted this turn of events, but they provided me with such a great experience. My hope is that this little story can show other young folks feeling the pressure of finding entry-level positions in avian research that it is possible to make a major step into this field on your own. I think unexpected interactions such as this aren’t so rare in the animal world. It’s encouraging to think that more dedicated observations of breeding birds by birders from all backgrounds can lead to new scientific insights. To see more photos of these interactions, check out my website!