TRUCKING WITH DOVES
A lady called this week worried about a Mourning Dove’s nest built on her truck. Yes, on a truck! She wasn’t worried about the truck, but about the flimsy nest and the high spring winds. There were already young birds in the nest. What to do? It seems unkind to say, but the best thing to do is nothing. It is all part of their strategy.
Most everyone is familiar with a common reproductive strategy employed by many plants. Millions of seeds are produced because so few survive. Mourning Doves are similar. In warmer areas, these birds may attempt up to six broods in a season. This fast breeding is essential because mortality is high. Each year, as many as 60% of the adults succumb and only about 30% of the young even reach adulthood.
Nests usually contain two eggs which will hatch in about 14 days. Eleven days later, the young will fledge. If you happen to watch a Mourning Dove nest throughout its cycle, you might notice that soon after the doves fledge, they are tended by only a single parent. That would be the male. He has already impregnated the female who is already sitting on the next clutch of eggs. And, those young on the truck? If they survived the winds and made it to adulthood—they may breed themselves in a few weeks.
Despite their remarkable fecundity, Mourning Doves are monogamous and form strong pair bonds. Pairs typically reconvene in the same area the following breeding season, and sometimes may remain together throughout the winter. However, lone doves will find new partners if necessary.
One of my favorite sounds is the soft cooing of a Mourning Dove. That’s one way it attracts or keeps its mate. But, if you pay attention to them this time of year, you will often see them flying up somewhat and then going into a circling glide. That is a flight display—part of showing off to attract a mate. Once the birds have mated, they build their flimsy nest. Typically, the male brings the materials to the female, who does the building—if you can call it that. [I have also found Mourning Dove nests on the ground—at least that keeps them out of the wind.]
So, how is this reproductive strategy working out? According to the North American Breeding Bird Survey, populations have slightly declined since 1966, Partners in Flight estimates the global breeding population at 120 million with 81 percent spending some part of the year in the U.S., 19 percent in Mexico, and 5 percent in Canada.
Mourning Doves also remain the continent's most popular game bird: hunters shoot as many as 20 million Mourning Doves each year. Because of the birds' popularity, game managers monitor their numbers to set hunting limits.
Although Mourning Doves seem to do well in the face of hunting pressure, they also suffer from a less visible problem of lead poisoning. Mourning Doves forage on the ground, and in heavily hunted areas they may consume fallen lead shot with the grit they normally use in digestion. Because one lead pellet can kill a dove, the assumption is that, perhaps, 5% die of lead poisoning. Even worse, in many cases, the carcass may be scavenged by a hawk or eagle which can also be poisoned by the lead. [If you are a hunter or are friends with one, remember to help out wildlife by never using lead ammunition. There are alternatives!]
Anyone who lived in Western Colorado ten years ago or before would have observed Mourning Doves as our only representative of this group. No longer! There have been invaders. Every morning this spring, I am hearing the soft plaintive call of a white-winged dove. There have been some around my neighborhood for several years. I have yet to find a nest, but I have seen one juvenile during breeding season.
White-winged doves are very common in the borderlands of the United States and even more so in parts of Mexico and Central America. Currently, they are expanding their range northward—a possible consequence of global warming. But, the inroads of the white-winged dove are paltry. As I reported in a previous blog (http://www.gjsentinel.com/blogs/birds_and_more/entry/fifty-two), during the Grand Junction annual Christmas count we found three this year, and have found them four of the past six years. Before that? Never.
The real invasion story, however, is the Eurasian Collared Dove. Less than forty years after its accidental introduction in Florida, this species is now one of the most widespread and abundant birds in the United States. In 2004, the Grand Junction annual Christmas count found zero. In 2013, we counted 593! These are the big doves in your yard that often sail around and land with a nasal hwahh.
Eurasian Collared Doves use a flight display very much like the Mourning Dove. Listen to their sound when they land and watch for the wide, white-tipped tail (http://www.bines/search?q=eurasian+collared+dove+invasion&qpvt=eurasian+collared+dove+invasion&FORM=IGRE). No one knows what to do about Eurasian Collared Doves. As an invasive, they are not protected. Hunters can harvest as many as they like. Unfortunately, they like living near people, and it can be difficult to find a location for safe hunting. Are they harming the populations of other birds—Mourning Doves in particular? This is a matter of much debate that probably won’t be settled until these species have lived together for a few more decades or longer. One thing is certain. Change in nature can be rapid, and man’s ability to conduct unplanned experiments seems to be unlimited.
Join one of Grand Valley Audubon’s Spring Bird Walks--every Wednesday and Saturday through May. Follow the GVAS Facebook page, the website (http://audubongv.org) or send an email to firstname.lastname@example.org to find out where to go and when to meet. There are “loaner” binoculars and checklists. You will learn a lot and have an enjoyable beginning to your day.