It’s getting late in the year for Michigan birds to still have young in the nest, but for a pair of Mourning Doves residing on a drain pipe outside Kensington Nature Center the season is still prime. Doves famously produce multiple broods per year and these doves are just putting the finishing touches on their third set of twins. Fortunately, these prolific birds are very tolerant of human gawkers, so they are quite photogenic. Put these two factors together and you have a late opportunity to see suckling squabs.
Normally, of course, the term “suckling” would exclusively refer to baby mammals – as in suckling pigs or suckling Snow Leopards – because baby mammals suck milk from their momma’s mammaries. This is a pretty exclusive club limited to haired organisms with teats. Although lacking in teats, members of the pigeon family also produce a form of milk to feed their young. As a matter of fact, these birds go one up on the mammalian model by providing a physiological method for both male and female pigeons to feed their young in this manner. There ain’t no male Snow Leopard alive that could (or would!) allow his young to suckle upon him.
We waited for some time at the dove nest to see this milking action take place. I say “we”, because a small group of folks had gathered around the spot by the time the event actually occurred. All it took was one person staring up at the nest spot beneath the eave to attract my attention. Soon a few of my naturalist friends joined me, along with some additional patrons, to admire one of the adult birds and its two chicks (from this point on referred to as squabs). We had quite a conversation going on in our small group, although I was trying to concentrate through my view finder. Fortunately the birds didn’t seem to mind too much, but I was fearful that our action would deter the other adult, and blow my chance to see the milking. Fortunately, someone finally asked “what do they feed their young?” and I mentioned milk. For some reason this quieted things down immediately as all (except the naturalists) pondered over the potential location of the nipples on a bird.
I should have explained that pigeon milk is made of “desquamated cells sloughed off the germinal epithelium of the crop” but, in all honesty, I did not have that phrase on the tip of my tongue at the time. Pigeon milk is a curdy yellowish liquid secreted from the pre-stomach pouch known as the crop. The substance is rich in protein and fat and compares favorably with cow’s milk. I found out later through my research, that it also smells like cheese. And, lest we forget within these few short paragraphs, both sexes produce and distribute it.
I initially snapped a few shots of the scene just to record the incredible ugliness of the squabs (they have big bright eyes, but their tubular nostrils are features that only a mother could love) and to admire their palatial nest. Mourning Doves are among the worst nest makers on the planet. They normally lay a pile of loose sticks down and call it “art”. These structures are normally so bad that you can look up through the bottom in order to count the eggs within (this number is always two, but you get my point). This nest, being the third in the same spot, was a solid mound of sticks rivaling any robin’s nest in the area (see here). There was nothing about this nest for the doves to mourn over, except for the fact that it was cemented together by ample applications of poop.
Eventually the other parent bird arrived on the scene. No one could be sure whether this was the male or the female, but in this case it didn’t matter. The bird sat on the edge of the roof for some time and nervously bobbed its head up and down. We eventually backed away to a respectful distance and she/he then flew into the nest. The adults switched places. The new arrival prepared itself for suckling as the first flew off to pasture.
Upon facing its charges, the adult opened its mouth and both young stuck their beaks down her maw. Doves suck up liquids, so it is no stretch to say that these young were suckling. Heads bobbed up and down for several uncomfortable-looking minutes as the hungry squabs eagerly ingested the crop contents. This was the first time that I have witnessed this act and I must say that I am glad to be a male mammal.
After the deed was completed, one of the squabs was left with a drip of liquid hanging off its beak and a seed stuck to the side of its head. Mom/Dad looked relieved and peace settled upon the poopy nest and its occupants.
The explanation of the seed is simple. In practice, Mourning Doves only feed their young pure milk for the first 3-4 days of their existence. For the next period, from 4- 12 days, the parents begin to introduce an increasing amount of seeds into the mix. They gradually wean their swabs of milk entirely after 12 days and from that point on exclusively deliver seeds. Since these squabs were both well along, it is likely that only a quarter of this feeding act actually involved milk and that the remainder was seed based. Sure, you could say that we weren’t witness to a true suckling event, but let’s not get all sucky about it.
By the way, the literature records that main feeding duty falls to the male parent after the squabs reach 16 days of age. If the dad doves ever figure out how to produce their own eggs they could take over the world (if they develop teats, then we humans will also be doomed).