Avian generations in the making – part 2A: nesting and man-made construction

Hi folks — today I’d like to share with you some of my observations on the second part of avian reproduction — the process in which birds make a nest and lay eggs. (By the way, if you look up “bird nesting” on the Internet, the search will lead you to a human activity: a shared custody arrangement where children reside in one house and the parents take turns living there with them. In the bird world, some avian parents will actually share a home, such as this very old and enormous sociable weaver nest (Philetairus socius) that I saw in Namibia.)

Females of a few species will deposit their eggs in the nests of another, such as some cuckoos and brown-headed cowbirds (Molothrus ater). Some people dislike cowbirds intensely because of their nest parasitism (the cowbird baby will hatch first and eat all the food or perhaps get rid of the other eggs or babies). I figure that this is how the cowbird evolved – it didn’t make a choice to wipe out other species so I can’t blame or hate the bird for it. But the cowbirds do appear to pick on particular species as involuntary “foster parents” and this may be affecting the success of the other species’ reproduction.

There are two general broad categories of bird nests – those located in or on man-made objects such as nest boxes, atop downspouts, in vehicles, in plant pots and other places and those constructed by birds in trees, shrubs and on the ground (i.e., the natural environment which I will discuss in the next blog so this doesn’t get too long!). When birds make a nest in a “human area”, people will often try to accommodate them, not using the object or vehicle or making the space safer. For example, when American robins (Turdus migratorius) put a nest on one of my downspouts, I covered the rainwater container underneath it so the fledglings wouldn’t drown when they leapt to freedom. (I did it just in time, too!)

Swallows and phoebes will also use human constructions as places to situate their homes. The cliff swallows (Petrochelidon pyrrhonota) gather up mud, making countless trips to wad up small balls of the material to carry back to a place like this pier at Cane Creek Reservoir where they line up their nests in a row.

   

Barn swallows (Hirundo rustica) locate their nests inside, using rafters to place a nest; they may end up sharing space with paper wasps and organ pipe mud dauber wasps (Trypoxylon politum), which doesn’t seem to bother them.

The Eastern phoebe (Sayornis phoebe) may use an inside corner of a patio overhang as a site that is conveniently accessible from outside.

Purple martins (Progne subis) living east of the Rocky Mountains almost exclusively nest in homes provided by people. The hanging gourd nests can be seen in fields but nowadays other types of plastic constructions are also used.

    

In order to attract barn owls (Tyto alba) back to areas where many traditional barns have been razed, people are also placing special boxes in fields with plenty of open space in front of them so that the owls will have a hunting territory adjacent to their front door. Made of heavy plastic, these boxes may be monitored by organized groups in an effort to document their use.

   

At the Mason Farm Biological Reserve, an eagle scout project involved bringing in cranes to attach very large nest boxes to the tops of trees for barred owls (Strix varia) – so far, I have only seen Eastern gray squirrels making use of these nests.

And then there are the nest boxes that people put up to attract Eastern bluebirds (Sialia sialis), brown-headed nuthatches (Sitta pusilla) and screech owls. In my yard, other birds use these boxes, too, including the Carolina chickadees (Poecile carolinensis) such as my one-legged,  banded friend Chantal, Carolina wrens (Thryothorus ludovicianus) who may puzzle about how to get a long twig into the box and house wrens (Troglodytes aedon), who pile up twigs in a rather untidy stack inside the box.

   

   

Chickadees construct lovely mossy nests lined with hair, fur or plant fibers.

      

The nuthatches have nests with bark strips.

    

Sometimes people will intervene when a nest is in danger. A Carolina wren put her nest into a boat at Cane Creek Reservoir that was rented out to people and keeping the nest there was not a good option as she would be missing her nest for hours when the boat was gone. The land manager was so kind as to relocate the nest into a tree right in front of the boat’s resting place; unfortunately, inclement weather caused the nest to dislodge that evening.

   

Another danger may also threaten the birds and their nests – predators. A friend and I found it unusual to see a tree swallow (Tachycineta bicolor) putting a nest in a bluebird box on the edges of a farm. Several days later, we saw a black rat snake (Pantherophis obsoletus) peering out of the box and the swallows were nowhere to be seen.

   

If you can manage to mount your boxes on poles rather than trees, put both squirrel and raccoon baffles on them and also place them away from overhanging branches, they should stay relatively safe from the squirrels, snakes and raccoons. Next up: birds’ nests with no human connections.

 

 

Avian generations in the making – part 1: courtship

The tragedies being faced in the Caribbean islands after hurricanes Maria, Jose and Irma are horrible and other than donate cash to help alleviate the needs, I’m not in a position to offer more assistance. I’m grateful for all those who can and hope government assistance will be forthcoming to help all the people in those nations recover.
The effects of the hurricanes also will be noticeable for the wildlife. Many of those living on land will drown or die of hunger; some birds may be a little luckier – able to shelter against the winds if they are native to a place or able to change their migratory pattern (e.g., delay arrival on wintering grounds) for a time. But when the effects of the storms are immense with lots of habitat destruction, the birds, too, will lack places to shelter and not have sufficient food supplies to survive.

It’s thought that some birds endemic to the islands may be severely endangered as a species. On 22 September, birders were happy to hear that eight Barbuda warblers (Setophaga subita) had been spotted on that island; not a lot but they may help ensure this tiny bird doesn’t become extinct.  At the time of writing this blog, the fate of some other bird species was still unknown. I hope that all the Caribbean bird species survive and will be thinking of them as I share this series with you on how birds take measures to ensure future generations. (It might seem odd to write this series now, but some birds are still feeding their young here.)

So, the process begins with courtship. Some birds mate for life, or at least form long-term (multiple-year) bonded relationships. They include bald eagles, black vultures, blue jays, Canada geese, white-breasted nuthatches, brown-headed nuthatches, Northern cardinals, Carolina chickadees, American crows, pileated woodpeckers and my favorite raptor shown above, the osprey (Pandion haliaetus).

Those who form ongoing bonds may have a courtship period that consists of the male bringing the female some food to indicate it’s time to get ready for nest-building. This was the case for these lovely Northern cardinals (Cardinalis cardinalis).

The American crow (Corvus brachyrhynchos) has a similar behavior; in my yard, I sometimes throw out bits of apple or bread for them in the spring as these seem to be considered real treats. The female will sit on a branch overhead calling until the male brings her some – and sometimes almost shoves it down her throat!

The Northern mockingbird (Mimus polyglottos) males will sing their repertoire in the spring to entice female mates – often they perch on the top of trees and fly up and down with spread wings in a beautiful display while singing.

        

   

The yellow-billed cuckoo (Coccyzus americanus) seeks new mates each year but has an interesting courtship behavior described by All About Birds: “A receptive female perches with its head up, pumping its tail slowly up and down…Just prior to mating, the male Yellow-Billed Cuckoo snaps off a short twig that he presents to the female as he perches on her back and leans over her shoulder. Both birds then grasp the twig as they copulate.”

 

     

 

The downy woodpecker (Picoides pubescens) females and males may both flutter between trees with slow wingbeats. Two females may also compete for the attention of a single male, a behavior I observed this past spring and which surprised me.

 

     

The male brown-headed cowbird (Molothrus ater) will vocalize for the female while spreading his wings in a display.

The killdeer (Charadrius vociferus) has a somewhat prettier courtship dance, bending forward and spreading its tail feathers to show off the colorful underside.

  

Next year, I hope to see more of the birds courting as it gives me a happy feeling.

The next step for the birds is nest-building. We don’t have the bowerbirds in North Carolina, who build elaborate nests as part of their courtship. But the species we have do spend a good deal of time on their nests and I’ll share some of their efforts in the next part of the series. (But one or two blogs on another topic will come first.)

 

Credit map: By Kmusser (Own work, all data from Vector Map.) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

Yay for the bluebirds!

Eastern bluebird Eastern bluebird IMG_9836©Maria de Bruyn resLast year was a disappointment for the bluebirds (Sialia sialias) and me when a cowbird (Molothrus ater) laid her egg in their front-yard nest. The cowbird hatched first and when I looked a few days later, the bluebird eggs were gone. The bluebirds dutifully cared for the foster child but had none of their own.

This year, they returned to the same nesting box and despite there being whole flocks of cowbirds around, they were able to avoid being surrogate parents this year. On 2 May, there were three eggs and by 5 May there were four.

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On 17 May, after mama and papa left the vicinity of the nest, I peeked in and saw the hatched babies, very naked newborns indeed! Mama was often with the babies and papa came to bring food, but mama left from time to time. They both visited the feeders to replenish themselves.

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I set up a canopy chair to observe at what I thought was a good distance but discovered I was too close. The parents would arrive in the tree fronting the nest but if I was too close in their opinion, they would not go to the nest or only after I had been still for quite a long time. It was interesting to see that they were feeding the hatchlings dried meal worms along with other insects that they had caught.
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They also seemed to be feeding the babies fruit – wild raspberries from what I could tell!

Eastern bluebird IMG_4994©Maria de Bruyn resBy 28 May, the babies were much larger and feathered. Mama and papa were kept busy ensuring they were well fed! And house cleaning to remove their brood’s fecal sacs was also a definite necessity!

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Eastern bluebird IMG_5371©Maria de Bruyn resThe parents remained very vigilant – not only keeping an eye on me but also other too curious visitors. On 1 June, a gray catbird (Dumetella carolinensis) suddenly descended to the nesting box, fluttering its wings furiously to remain suspended in front of the hole while it looked in. It then flew up on top of the box but the bluebird adults chased it away VERY quickly!

 

Eastern bluebird IMG_5008©Maria de Bruyn res

 

 

By 2 June, the babies were looking ready to fledge. The next day, I had time to watch the box and saw a baby repeatedly looking out (but not really calling much).

 

 

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Sure enough, I saw it leap and swoop up to perch on a nearby branch.

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The next baby soon began peeping out, too, although this one also retreated inside the box now and again. Eventually, this baby swooped out as well, but s/he flew all the way across the street to a neighbor’s yard. When I carefully looked inside the next box, I saw that they were the last two to fledge – the others had gone before.

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Oddly, I haven’t seen the babies at the feeders although I see the parents there.

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Eastern bluebird IMG_8749©Maria de Bruyn resThey or another bluebird couple were checking out a nest box in the backyard. They didn’t use this one (Carolina wrens have moved in with a nest there in the last few days) but they have constructed a new nest in another backyard box today. So I hope to witness another fledging in a few weeks! Yay for the bluebirds!