The crying of babies. Is there any other sound that commands the attention so completely? There is a need to be met, and the penetrating cry of a baby makes this abundantly clear to all within an amazing distance.
The same is true in the bird world. The crying (begging) of a baby bird is not to be ignored. It prompts parents to ever greater efforts to feed the hungry young.
However, there has been a sound missing this summer. The plaintive cries of young red-tailed hawks have been largely absent. Most years July and August resound with the complaints of recently fledged young. The sounds grate on the ears, but it is the sound of a new generation of red-tailed hawks experiencing tough love from their parents.
From hatching to fledging, the parents provide all the food for the growing young. Even after they fledge, the parents continue to meet the needs of the ravenous offspring. However, after a couple of weeks, the adults begin to cut back on the provisions. The young are less than happy with the change, and they complain.
It is time for young to begin to provide for themselves. If a young bird wants a full belly, it will need to top off its tank by catching something of its own. This is a weaning period, where the parents gradually provide less and less food over the next few weeks. Young birds need to sharpen hunting skills quickly to make the transition to independence. As a general rule, two out of three young die before their first birthday. Most die in the first few months because they don’t master the needed hunting skills. Being a successful predator is not easy.
This year has been different. I heard no complaining. Summer afternoons have been filled only with the calls of collared doves. I have seen only one fledged young from the dozen or so redtail nests I follow informally. It was the same last year, and to a lesser extent a couple of years before that.
Red-tailed hawks have hit a rough patch. We are not in danger of losing our redtails, but I do wonder what is happening.
When a predator has problems, I first look to the prey. There is certainly no shortage of gray diggers (California ground squirrels). Since the gray fox population took a hit a couple of years ago due to disease, the squirrel population has exploded. My yard and garden can hardly wait for the return of the fox.
No. Something else is missing, at least in my yard. I haven’t seen a meadow mouse (California vole) in several years. Vole populations typically go boom and bust in roughly a four-year cycle. A prolonged stretch of low numbers is unusual. Voles feed low on the food chain, mostly green vegetation and are not as vulnerable to changes in their food supply or as sensitive to pesticides and such. I don’t know what is happening here.
I’m not sure low vole populations are responsible for the low reproductive success of red-tailed hawks in the valley, but I wonder. For now I am left to wait for another year, and dare I say it, the return of the meadow mouse.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.