Ask SIB: Eastern Bluebird Winter Behavior

On January 9, 2021, Andy wrote SIB, “Today we saw maybe half dozen blue birds and one was sitting on the entry hole.  Isn’t it early for them to be nesting?  Has the warm weather put them off schedule?”

Eastern Bluebird – photo by Bob Mercer

The questions are relatively easy to answer. Yes, it is too early for them to be nesting, so they are not “off schedule” due to the weather. As usual, the questions lead to another question; what are the birds doing?

Since Eastern Bluebirds are year-round residents in our area, one can watch the full range of behaviors. During the winter months, bluebirds can gather in flocks of up to 20 birds. These flocks consist of one or more family units. In really cold weather, a flock of bluebirds may all cram into a single cavity, presumably for shared body warmth. Pair bonding for bluebirds can happen anytime between November and March.

This photo of an Eastern Bluebird entering the box and the female watching perfectly captures some of the courtship behavior–wing droop tail spread. Photo by Nancy Brown

During the courtship and nesting period, the flocking behavior disappears. Once a pair settles on a territory, they work hard to drive away all competitors including their siblings. 

It is difficult to know exactly what Andy observed, but one can make an educated guess. Since he saw a half dozen birds, he observed a winter flock. The bird sitting at the nesting hole most likely was a male bird checking out the box for its potential. 

Once a male makes a choice, he will then attempt to attract a mate or to solidify his relationship with his current mate. According to the Cornel Lab of Ornithology website Birds of the World, the male goes through a very predictable pattern of behavior. The male institutes a nesting demonstration display where he perches at a hole holding nesting material with his wings drooping and his tail spread wide. He looks around, presumably to make sure his intended is paying attention, and then look in the hole. The next step is to rock back and forth into and out of the hole before going in the cavity. Once in the cavity, he will stick his head out still holding the nesting material. Leaving the material in the cavity, he then hops out near the hole and does a wing waving display. The female entering the box cements the pair bond. 

People with bluebird boxes they can view, or who have cameras trained on a box, may be lucky enough to watch this behavioral sequence. 

Nesting on Seabrook Island usually begins around the first of March. The Seabrook Island Birders sponsor a bluebird box monitoring program. Volunteers have a route where they check a series of boxes once a week to monitor if birds use the boxes and nesting success of failure. Anyone interested in helping is encouraged to contact the Seabrook Island Birders.

Be sure to read tomorrow’s article discussing the installation and monitoring of a birdhouse with an outside WIFI camera!

Gowaty, P. A. and J. H. Plissner (2020). Eastern Bluebird (Sialia sialis), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Ask SIB: “Are Red Knots at North Beach?”

Fred Whittle recently sent a question to Seabrook Island Birds. He asked, “Are Red Knots at North Beach now?  Thought I saw them on Sunday afternoon.”  

Photo taken of Red Knots and other Shore & Seabirds by Mark Andrews on 12/28/21.  Notice the misty view, as there was a thick marine layer with visibility of only around 50m date day.

The quick answer is yes. Mark Andrews recently reported 300 birds at the end of North Beach. That leads people who like birds to a host of other questions. First and foremost, “Why are they here?” Instinct drives much bird behavior. The hard-wired drive to migrate makes birds leave the far north long before conditions become untenable for life. Some but not all of the eastern race of Red Knots, Calidris canutus rufa, migrate from the Central Canadian Arctic to Tierra del Fuego at the southern tip of South America. With studies being done by scientists and observations like birders on Seabrook Island, much has been learned about Red Knot migration habits and much more still needs to be discovered. Knots spend winter in four regions:

  1. Southern coast of S. America, mainly Tierra del Fuego
  2. Northern coast of S. America, mainly Maranhão
  3. Western Gulf of Mexico, mainly the Laguna Madre
  4. Southeast U.S./Caribbean, mainly FL to NC

Evolution created these four regions as ways to protect the populations. Each location offers advantages and disadvantages—e.g. long or short distance to travel low or high parasite exposure. Unfortunately, a evolutionary new risk has arisen in these ancestral wintering grounds—humans. Development along the migratory route and probably climate change stress the migrants. 

The work being done by SCDNR, University Of South Carolina’s Senner Lab, and our local birders strive to understand if the same birds each year hang around South Carolina or are they stopping here on their way to Florida or farther south. We do know that the numbers of Red Knots slowly increase as the season passes into spring. We do know that many of our birds spend time in Florida and when they arrive here, they may stay several weeks of even months before flying on to either New Jersey’s Delaware Bay or directly to the southern tip of the Hudson Bay.

In May, birds with flags indicating that they were banded in South America show up on Seabrook Island. They join up with the birds already here before they all depart sometime before Memorial Day.

For all these birds, the arc along the South Carolina coast provides a critically important stopping area where they can pack on the fat before tackling the long flight to the Arctic and the arduous task of raising the next generation.

When you see people out on the beach taking pictures, recognize that the photographers want far more than pretty picture, they want clear images of the tiny flags on the bird’s legs. Once scientists receive these flag codes, the scientists can start to build a better understanding of the migratory patterns of the Red Knots.

When you are on the beach, remember, “Share the beach – give them space!” If you have questions or are interested to learn more about the SIB Shorebird Steward team, please send and email to: or complete this form.

Ask SIB: What is this Bird and How Can I Prevent Birds from Flying into Windows?

QUESTION: Hi! This beautiful bird has been visiting at regular times every day for a month. He keeps flying into the same two windows – we’ve tried using reflectors, etc., but he’s undeterred. He usually hangs out with the Northern Cardinals, but oddly, he never joins them at our nearby feeders!

Thanks for any info!

Jenni Hesterman, SIB Member

ANSWER: Hi Jenni – This beautiful bird is a Great-crested Flycatcher. They are not known as a feeder eating bird. See the description below from the app iBirdPro for their feeding and foraging habits.

“Great Crested Flycatcher: Eats variety of large insects, including beetles, crickets, katydids, caterpillars, moths, and butterflies; also eats fruits and berries; forages by flying from a perch to snatch insects from foliage, mid-air, or on the ground.”

Learn more about the Great-crested Flycatcher here:

There are many suggestions on how to prevent birds from flying into your windows. Understandably, many of us do not want to give up our views by installing heavy draperies or applying sticky notes every two inches. If you are serious about finding alternatives, there are some less obtrusive solutions. Check out the link below for some ideas and also read the comments from other bird enthusiasts. Some people have had success by simply moving the location of their feeder or not cleaning their windows. Now, that’s a win-win! 

Nancy Brown & Joleen Ardaiolo, SIB Board Members

Ask SIB – More Birds Mobbing


Hi, Today I was walking not far from a pond with high reeds.  A big heron was standing on the ground minding his own business when suddenly a red wing blackbird exploded out of the reeds and attacked the heron.  The big guy took off  and the red wing kept after him for twenty or thirty yards.  I assume the red wing was protecting a nest but do heron eat bird chicks?

Andy Allen, SIB Member
Red-winged Blackbird mobbing Great Blue Heron, by Larry deWitt;


This interesting observation contains two parts based on the behavior of each bird. The Great Blue Heron is an opportunistic feeder and will eat anything it can get down its throat. This would presumably include Red-winged Blackbirds. Red-winged Blackbirds tend to be an aggressive species defending a territory against other Red-winged Blackbird and occasionally against predators. A male Red-winged Blackbird defends a territory as opposed to a mate. It is not uncommon for a strong male to hold a highly desirable territory which attracts numerous females. Therefore, the bird you saw chasing the heron was not defending a particular nest, but driving the bird from his territory and presumably his harem of females.

Mobbing, the behavior of chasing away a potential predator is a common behavior among many bird species. Is it innate or learned? I don’t believe anyone has studied the Red-winged Blackbird’s interactions. A surreptitious study by Konrad Lorenz and detailed in his book King Solomon’s Ring details how Rooks, a European species of crow, which he fed by hand, instinctively attacked his hand when he was holding a limp black object (similar to a dead Rook).

He tested this behavior on captive birds and learned that after the bird instinctively attached something holding a limp black object on three occasions did it learn to always attack that object. The final piece of the puzzle is once a bird learned to attack an object, it taught its progeny to attack that object even if they never saw the object holding something limp and black. For the Rooks, the behavior is both instinctive and learned. Maybe it is similar with the Red-winged Blackbird as they have been documented attacking tractors, cows, and horses, all things that might intrude into the birds habitat.

Bob Mercer, SIB’s “Resident Naturalist”

Ask SIB: Do Birds Cooperate to Chase off Predatory Birds?

Question: I saw something that that I thought interesting . We have a blue bird box and a Carolina Wren nest around 50 feet apart. A large Crow landed on the Bluebird box. Both the males attacked the crow to drive it off. Were they working together or as individuals? The Bluebird stood on the top of the box, the Wren on top of its nest. Chipped to each other and entered their nest. Were they communicating with each other?

Anonymous SIB Member
Crow mobbed by Baltimore Oriole in White Clay Creek State Park, Delaware.
Photo from Buffalo Bill Center of the West.

Answer: What a cool observation! Normally, it is a House Wren that occupies a bluebird box. House wren are very aggressive and will even destroy a bluebirds eggs if it can. 

So normally, bluebirds do not tolerate having a wren nest nearby, unless the nest opening is too small for the bluebird. This leads me to believe the birds were not cooperating. Normally, both birds work to drive away predators. Nest predation is a major challenge for birds and crows are notorious for feeding on baby birds. Both the bluebird and the wren don’t want a crow nearby. So both would be inclined to attack the crow regardless of what their neighbor does.
This brings us to the second part of your question. Since the bluebird naturally competes with a wren, I suspect that the “communication” you saw was neighbors grousing at each other as opposed to bragging about their ability to chase a crow.

Recognizing that crows are highly intelligent birds, I bet this will not be the last time they visit. I suspect the crow will work hard to access the known food source-baby bluebirds and wren-either directly from the nest or waiting until the babies fledge. This is one reason why, as soon as babies come off the nest, the parents try to get them as far away from the nest and as SIB’s “Resident Naturalist”quickly as they can. 

Bob Mercer, SIB’s “Resident Naturalist”

Ask SIB – Size of Opening for a Carolina Wren Nest Box

QUESTION: Every year Carolina Wrens nest in my front and backyard, either in the hanging plants, generic birdhouses I’ve received as gifts, etc. This year I bought some wren houses from Woodlink but the opening is only 1″ round. In googling it, I see “expert” sites contradicting themselves – recommending 1 1/8 or 1 1/2 or larger, depending on whether attracting House Wren, Carolina Wren, etc.) Anyone know what size I should enlarge it to?


ANSWER: Good question, which is my statement any time I do not know an unequivocal answer.

I do know that Carolina Wrens are opportunists nesting in cavities or any tight area like a planter as Mary has experienced, crotch of a tree, old pair of pants hanging in a garage (personal experience), or vine tangles. They can nest in a box with a 1 inch hole or a box up to a 1.5 inch hole, the recommended size for the Eastern Bluebird or larger. Most places recommend a 1 1/8 inch hole for Carolina Wren and 1 inch for House Wren. One of the primary reason for having a small hole is to prevent House Sparrows and European Starlings from using the nest. Neither of these species are an issue on Seabrook Island.

Choosing a larger hole opens up the potential for a variety of species to use your box.

Regardless of the size hole chosen, one may find that the House Wren will eventually usurp the box, most often filling it to the brim with sticks so the box cannot be used by other birds. Unlike the Carolina Wren, the House Wrens have a strong preference for nest boxes and more open, less shrubby areas.

One of the way to manage and encourage Carolina Wrens is to be ready early in the season. They should be laying eggs by mid-March. The House Wren will not be laying eggs until the first of May. This behavior allows the Carolina Wren to have its first brood prior to the House Wren even starting. The Eastern Bluebird starts in Mid-February.

Hope this helps.

Bob Mercer, SIB’s “Resident Naturalist”

Ask SIB: What Species are “Henry & Henrietta?”

Lake House resident Red-shouldered Hawks, Henry & Henrietta

Question: Does anyone know definitively what type of hawks are pretty much living behind the Lake House? I’m thinking red shouldered, since tail has black and white bands when flying. I call them Henry and Henrietta.

They can often be seen sitting on the bird house next to the lake, or on the roof, or the slats outside the exercise room. Today one of them perched there and then bent down and peeked inside at Melissa teaching.

Diane Allen, SIB member

The answer is a Red-Shouldered Hawk. You can learn more about this beautiful bird of prey by visiting the Cornell Lab of Ornithology “All About Birds” website. On Seabrook Island, they are often seen year-round near the Lake House, at the Equestrian Center and near the Recycling and Garden area.

Ask SIB if you have a bird related question.

Ask SIB: Where Have All the Pelicans Gone?

Sofia, 13-month old granddaughter of Dick & Marg Wildermann

SIB Received this email on Sunday 8/16/20:

Dear SIB

Our daughter has been renting a villa on Rolling Dunes, next to boardwalk #1, for two weeks.  We spend part of most days there, especially in the evening.  For two weeks, our 13-month old granddaughter, Sofia, loved being out on the porch or deck in the evening to watch the pelicans fly directly overhead.

The pelicans came over constantly, in groups of several or even 20 or more. We’ve noticed when walking the beach as well that there are many pelicans this year.

Well, Saturday evening there were very few pelicans flying over their villa in the evening.  On Sunday there were none.

Where have the pelicans gone? 

Sofia will be here for another week.  I promised her that SIB would bring the pelicans back.  So you now bear a heavy burden.  

Thank you,

Dick Wildermann

And then we received this follow-up note on Monday 8/17/20:

SIB friends:

We took Sofia to the property owner’s pool at North Beach today and there were lots of pelicans.  Thank you so much for taking care of our problem so quickly.  Sofia would point at them flying overhead and screech.  She loves pelicans.

I told her the SIB experts said we saw no pelicans yesterday because it was Sunday and they had taken the weekend off.  I hope that was the right answer.

Keep safe, Thank you, with love, Sofia

Dick Wildermann

Her mom, Jodi added,

Thanks! She’s a real birder already. She loves nothing more than the birds, especially the pelicans. She hasn’t learned yet that screaming at them chases them away rather than attracting them though.

Jodi Simopoulos

Besides having the weekend off, the only other explanation we at Seabrook Island Birders came up with is that the weather had changed and the Brown Pelicans had different flight patterns as directed by the Pelican Air Control (PAC). But in all seriousness, as this is a question many of our island residents and guests have asked, there probably is no logical reason we mortal humans could discern. Weather, tide, winds, fish schools, … all would have a bearing the pelicans would understand.

Ask SIB: Why is this Northern Cardinal Doing This?

This is a common question we receive from Seabrook Island Birder (SIB) members! Have you ever seen this behavior at your home?

We have a female cardinal that continues to try and get into the house. Generally 3-4 times a day she flies up the window sometimes she perched on the sill looking in. This has been going on for over four months.

Christine Dennis

For starters, rest assured the bird is not trying to get into the house. During the breeding season, birds aggressively attempt to drive off intruders of the same species. This is an instinctive behavior and not something the bird can control. What you are experiencing is a bird that sees its reflection in your window and instinctively attempting to drive the intruder away. The process follows a pattern. First the bird sees its reflection. Thinking it is an intruder, it displays a warning posture. Needless to say, the reflection responds with the same threat. This quickly accelerates to a full out attack. This is not something the bird can understand or learn not to do. 

The solution is to change the reflectivity of the surface the bird is attacking. This is easier said than done! There are several things you can try, none of them visually appealing. Some people have had success with strips if different color paper taped on the inside of the window  to break up the image. Completely covering the reflective surface on the outside works, but it also blocks the window. Installing screens will break up the reflection and soften the blow if the bird does hit the window. Finally, some people tie moving objects, pie tins, ribbons, etc., around the area to create movement that scares the bird away.

All that said, the bird will not hurt itself, will not break or damage the window, and will stop eventually when the breeding season ends.

Bob Mercer, SIB’s “Resident Naturalist”

Thanks to dlinnehan, we found this video on YouTube which provides great footage of both male and female North Cardinals attacking their own reflection.

Seabrook Island Birders (SIB) welcome questions from our community of birding friends! If you have one, just fill out the form on our website or send us an email!

Ask SIB: How to Keep Ants off the Hummingbird Feeder

Is there any way to keep ants out of my Hummingbird feeders? There is a little cup in the middle that is supposed to keep them out but nonetheless they crawl in through the ports, then get trapped and most of them drown.

Melodie Murphy

To keep ants off of a hummingbird feeder, you need to create a water baffle. If your feeder is a hanging feeder, they sell them wherever you get your feeder supplies. Essentially,  you are placing a small reservoir of water between the hook and the feeder. The ants cannot get passed the water. This needs to be kept full.

Bob Mercer

Seabrook Island Birders (SIB) welcome questions from our community of birding friends! If you have one, just fill out the form on our website or send us an email!

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