SIB

Several years ago and for several years we used to see a mating ritual among a class of terns in mid Spring. We saw it down at the point by the beach club but they would also appear over our Sealoft villa. The ritual was something like this. A female (I assume) tern would take off and start climbing and be quickly joined by two other terns (I assume males). She would do really intricate maneuvers- barrel rolls, inside-outs, etc. and the two pursuers tried to copy her. After several minutes of this she somehow would indicate her choice and the rejected bird would fly away. Then the couple did even more extraordinary maneuvers, diving, climbing, rolling, etc. and covering a lot of air space from the beach club out to over the Sealofts and back. They were always in perfect sync with one slightly behind and to the side of the other. It was extraordinarily beautiful, better than any ballet.

Questions: Is this standard behavior for a certain class of terns? Does it go on wherever these terns mate or is it peculiar to our coast? Which terns are these? What month are they most likely to do this?

Thanks for your feedback

Andy Allen

Answer:

Without knowing which species of tern Andy saw, it is challenging to make a definitive statement. Yet, Andy did provide some useful clues with his careful observations. To start at the basics, there are five species of terns likely to breed on or near Seabrook Island: Royal Tern, Forster’s Tern, Least Tern, Sandwich Tern and Gull-billed Tern.

Two of these species, Gull-billed Tern and Least Tern, tend to make more horizontal flights during pair bonding. So, we will rule out those species.

Forster’s Terns generally nest in the marshes, so we may want to rule out the Forster’s Tern, though it is worth understanding how they interact during pair bonding. The Royal Terns and Sandwich Terns nest on Deveaux Bank.

Most species of tern perform flights called “Dreads.” This is where a whole flock lifts up and flies around, not just because of a nearby predator, but as part of pair bonding and colony cohesion. The Forster’s Tern, Royal Tern, and Sandwich Tern have courtship flights described as “High Flight.”

What I believe Andy is referring to would be the “High Flight” behavior. That leaves the three species, Royal, Forster’s and Sandwich Terns. Here is how the scientists who wrote the pages for these terns on Birds of the World describe the variation in each species “High Flight.”

Forster’s Tern: “Two terns (sometimes 1 with fish) begin circling ascent in “jerk-flying” (Baggerman et al. 1956) manner (wings angled back with pause [jerk] at bottom of downstrokes, wing beats at faster rate [3–4 beats/s] than normal flight [2–3 beats/s]) up to 200 m. At highest point, leading tern starts gliding descent in Aerial Bent Posture (beak pointed downwards, black cap tilted away from other tern, wings held above horizontal); second tern performs Pass (gliding low over first tern) and adopts Straight Posture (beak forward, head tilted so black cap points away from other tern), initially fast and steep; Pass may be repeated. High flight may begin from ground or from flight. Terns may be silent or utter calls during Ascent. Fish-carrying tern most often the individual performing Aerial Bent Posture. After landing, if first tern was fish-carrying individual, that individual feeds the other during Posturing or Parading (see below; MKM).”

Royal Tern: In High Flight, one, presumably male, spirals upward, giving Advertising-Call, pursued by ≥1, commonly 2 individuals. During ascent, leader also gives Aack Calls, as do pursuers. Where >1 pursuer, these may pair off and continue own High Flight. Fish sometimes passed between 2 flying birds that have paired off, one dropping it a short distance to other below. Third may join and replace one of 2 original participants or cause 2 to break off aerial courtship. At peak of ascent (≥100 m), leader initiates downward glide, closely followed by pursuer. Both describe spiral descent during which Pass Ceremony may occur, as in Sandwich Tern. High Flight may last up to 25 min and lead to ground courtship, but pair more often retires to fish or to loafing flock to rest, preen, or bathe. Aerial courtship diminishes at hatching time, but occurs throughout breeding season.

Sandwich Tern: Usually aerial display follows ground courtship. An unmated male flies around a flock of loafing birds, usually carrying a fish and vocalizing in advertisement. He may alight on the ground near the flock and raise head and bill while calling, with wings held away from the body and crest raised. When female approaches, male takes off in an aerial “bent posture,” with head and bill pointed toward the ground and back arched. Female may or may not follow male into “high flight” display, and other birds may join in. Aerial courtship consists of ≥ 2 birds ascending in a circle for one to several minutes; at the apex, one bird breaks into a fast downward “glide,” often after several false starts. In the glide, the birds fly close together and trailing bird may overtake lead bird.

The short answer to Andy’s questions are as follows.

1. This is a standard behavior of many tern species.
2. It goes on wherever terns congregate.
3. The above descriptions lead me to believe that the birds Andy refers to are Royal Terns (though his assumption is about sex is wrong) as the behavior he described more closely matches that of the Royal Tern, though Andy did not mention if the birds were noisy or not.
4. The Forster’s and Royals are already here. The Royal Terns are pair bonding and setting up nesting territories in early April into May. The Forster’s Tern is mid-April to mid-May. The Sandwich Tern, which should be arriving in the next couple weeks, would be displaying in late-April to early-May. I do have to add that the first Least Terns, a SC Species of Concern should be arriving on Seabrook Island in about a week. Least Tern numbers grow through May. Each year, we have high hopes that a colony will once again establish itself on North Beach. Be sure to watch the antics of this species, but stay well out of their way so as not to disturb them!

One of the joys of living on or visiting Seabrook Island is being able to watch the birds and the bird behavior. We would love to hear from people who observe any of the above behaviors.

References:

Buckley, P. A., F. G. Buckley, and S. G. Mlodinow (2021). Royal Tern (Thalasseus maximus), version 1.1. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.royter1.01.1

McNicholl, M. K., P. E. Lowther, and J. A. Hall (2020). Forster’s Tern (Sterna forsteri), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.forter.01

Shealer, D., J. S. Liechty, A. R. Pierce, P. Pyle, and M. A. Patten (2020). Sandwich Tern (Thalasseus sandvicensis), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.santer1.01

• – Bob Mercer, SIB’s “Resident Naturalist”

You spot a hawk, but you’re not sure what kind of hawk you’re seeing. Is it a Cooper’s? A Sharp-shinned? Red-shouldered or Red-tailed?

If you’re out birding and listing your sightings in eBird then you definitely want to know exactly what you’re looking at, in order to correctly report your sighting. Need some help to polish your hawk identification skills?

Here’s a great article from Birds & Blooms magazine with 5 tips to help you identify hawks accurately.

https://www.birdsandblooms.com/birding/hawk-id-tips

Do you have photos of hawks you’d like to share with Seabrook Island Birders? Send your photos to us and we’ll share them on our Instagram and Facebook pages. Email your pics to gabbygirl29455@gmail.com.

Happy Birding!

Article Submitted by: Gina Sanders

Eastern Screech Owl – Megascops asio
Length: 6.3-9.8 in. Weight: 4.3-8.6 oz.
Wingspan: 18.9-24 in.

If you find yourself in a wooded area at night, don’t be too alarmed if you hear a haunting whinny floating across the night air. No, it’s not a ghost horse, it’s likely coming from a bird no bigger than a pint sized glass – an Eastern Screech Owl. In fact, hearing this owl is probably easier than seeing him as they’re well camouflaged and hide out in nooks and crannies of trees during the day. Your best chance of seeing one is to keep your eyes out for smaller birds causing quite the commotion. Blue Jays, Chickadees and Titmice will often mob a screech-owl (or other raptor), swooping around it with noisy calls. This can be enough of a nuisance to the owl to make him move on, and it alerts other birds to the predator’s presence.

They have two color-morphs, rufous (reddish-brown) and gray, with the rufous coloration making up one-third, and more common in the East. No other North American owl has such distinctive plumage differences. They have small ear tufts and yellow eyes, strongly streaked upperparts and finely barred and streaked underparts, giving them their excellent camouflage.

Eastern Screech Owls are found wherever trees are, from the Rocky Mountains to Canada to Mexico. Because they readily habituate to people, Eastern Screech-Owls sometimes roost and nest in human-made cavities such as bird boxes. They nest in holes and cavities but never dig a cavity themselves. They depend on tree holes opened up and enlarged by woodpeckers, squirrels or wood rot. Because old, dead or dying trees are often removed from yards, they’re sometimes short of nest sites and have been known to nest in wood piles, mailboxes, or crates left on the ground. They’re fearless defenders of their nest and will even strike unsuspecting humans on the head as they pass nearby at night.

Eastern Screech Owl pairs are usually monogamous and remain together for life. Nesting occurs between March and June. Females incubate 3-5 eggs for 30 days, feed nestlings for nearly as long, and then tend the fledglings for 8-10 weeks. Their diet is the most varied of any North American owl, to include a variety of songbirds, mice, rats, squirrels and rabbits, and a surprisingly large number of earthworms, insects, frogs and lizards. When prey is plentiful Screech-Owls store extra food in tree holes for as long as four days.

Small but mighty, Eastern Screech-Owls are mainly active at night, though they often hunt at dawn or dusk. They sit and wait in the trees for prey to pass below, then pounce from perches six to ten feet off the ground. In addition, suburban screech-owls often survive better than their rural cousins, as suburbs provide more prey and fewer predators. Their small size, territorial tolerance, and broadly varied diet make this owl a successful survivor.

Screech Owls are on Seabrook Island but as stated earlier, are rarely seen. A pair raised their young in a tree near the bird feeders at Camp St. Christopher several years ago. One was heard prior to a walk in the Maintenance area but wasn’t seen. Below is a picture taken on a visit to Brookgreen Gardens in February 2023.

To read more, go to: https://www.allaboutbirds.org/guide/Eastern_Screech-Owl

Submitted by Gina Sanders
Photos from National Audubon Society and The Cornell Lab All About Birds

This blog post is part of a series SIB will publish on a regular basis to feature birds seen in the area, both migratory and permanent residents.  When possible we will use photographs taken by our members.    Please let us know if you have any special requests of birds you would like to learn more about.

To register click here!

Friday March 24, 2023  8:30 am – 10:00 am
Location:  Meet at First Lagoon on left
Max:  20
Cost: Free for members; $10 donation for guests – Priority will be given to prior waitlisted & members

We’ll be exploring the birds seen along Jenkins Point lagoons and streets, including wading birds, shorebirds, song birds and possibly ducks.  We’ll go from location to location via car or bike.  Since this event can be primarily by car, it is appropriate for members with mobility issues.  Meet at Jenkins Point Ct., the street after the first pond on the left.

As always, be sure to bring your binoculars/cameras, hats, beverage and sunscreen.

If you’re not yet a 2023 SIB member, you must first become a member for only $15 by following the instructions on our website: https://seabrookislandbirders.org/contact/join-sib/. You may bring the form and your dues to the event. Or you may pay the Guest Fee of $10.

In mid-February, I saw a bird for the first time on Seabrook Island – an Indigo Bunting. I didn’t recognize it initially with it’s brown plumage with just a hint of blue. After about a week, it disappeared to return mid-March. Boy, what a difference now that he was in his breeding plumage. The pictures were taken through a window but they still clearly show the difference.

I know several “Yankees” who didn’t initially recognize our wintering American Goldfinch in their drab plumage. About the same time as my Indigo Bunting returned, I saw an American Goldfinch in his summer finery. These changes caused me to research more about molting. The Cornell Lab’s All About Birds site provided an excellent article: The Basics: Feather Molt. The first few paragraphs answered a lot of my questions:

A feather is a “dead” structure, analogous to hair or nails in humans and made of the same basic ingredient, the protein keratin. This means that when they get damaged, feathers can’t heal themselves—they have to be completely replaced. This replacement of all or some of the feathers is called molt. In addition to providing a new set of healthy feathers, molts often provide a new look to the bird’s plumage—new colors or patterns that can indicate the bird’s age, sex, or the season of the year.

Molt is extremely variable. Observed patterns can vary by species, by individual, from year to year, and by individual feathers on the same bird. Molts can be either complete, in which the bird replaces every one of its feathers over the same molt period; or partial, in which the bird replaces only some of its feathers (for example, flight feathers or body feathers).

Molt keeps birds in top flying condition by replacing feathers that have become worn or damaged with completely new feathers. However, if a bird loses an entire feather, that feather will begin growing back immediately rather than waiting for the next molt. (This is why people clip the flight feathers of captive birds rather than plucking them out.)

Molting occurs in response to a mixture of hormonal changes brought about by seasonal changes. The entire process is complex and many questions remain regarding how the process is controlled. A basic understanding of molting patterns can be a useful aid in identifying many species and in determining their age.

Timing
It takes a lot of energy to build new feathers. As a result, timing is important—and birds typically time their molts to avoid other periods of high energy demands, such as nesting or migration. Molt timing can be more complicated for larger birds, because growing larger feathers means that their molt process takes longer than it does for smaller birds. This is one reason why some birds undergo partial molts.

I encourage you to read more about this feature of our feathered friends but reading the entire article The Basics: Feather Molt by Cornell Lab’s All About Birds.

Submitted by: Judy Morr

“Did you know” is an on-going series of blogs that answer possibly more technical questions people have about birds or their environments. If you have an idea or question, submit it via the “Ask SIB” link on the SeabrookIslandBirders.org web site or send an email to SeabrookIslandBirders@Gmail.com.