by Dave Grant
Four white wading birds are encountered on the east coast: the cattle egret, great egret, snowy egret, and the little blue heron, in its immature phase. Each has distinctive features like size or leg and bill color, that allow even inexperienced birdwatchers, with a little practice, to distinguish one from the other. But just as distinctive, and almost as reliable a key, is the behavior each exhibits in its daily search for food. By learning a few tips, birders can often differentiate these four similar waders at a considerable distance.
Studying behavior is an important aspect of birdwatching and oftentimes the most entertaining part of it. If you take the time to follow wading bird activities for an hour or two, you will be well rewarded for your patience and discover that when it comes to finding food, they have developed an extensive and amusing repertoire, exploring, it would seem, every conceivable fishing technique. Such flexibility has helped this showy group of birds to reoccupy most of the range they were extirpated from at the turn of the century. Today you can even find them in some of our smallest and least pristine waterways, and they always add a certain wildness to any body of water, regardless of its location.
Although waders require more privacy and space around their rookeries than many smaller birds, quiet birders do not disturb these stately fishermen while they are feeding. This provides plenty of opportunities to enjoy their fishing antics and see how several very similar-looking species can seem to occupy the same niche, yet manage to avoid too much direct competition with each other.
Cattle egrets are the smallest,
most gregarious, and the most terrestrial of the group. They
are likely to be found hunting insects, amphibians, and small
animals along roadside ditches or on shorelines and of course,
near cattle, which flush lots of small prey. Since cattle and
even dairy cows are less plentiful than they once were, it's
difficult to find such a scene locally. But the egrets sometimes
make do using work vehicles like tractors as beaters to stir
up their prey.
While not adverse to wading, cattle egrets tend to keep their feet dry and because of this preference are easy to tell apart from the other three species of waders at a good distance. They actively stalk their game in belly-deep grass, and this is the best clue to identifying them at a distance. During dry periods the little blue heron and the snowy egret may be found occasionally in grasslands too, but their darker bills and more slender figures helps identify them.
In the water, the little blue heron is an active hunter, moving at a deliberate pace through the shallows to strike at unsuspecting fishes. They are much more animated than their large cousin the great egret, which, like the great blue heron walks slowly through the water with its neck thrust out at a 45 degree angle, or freezes into a rigid pose and waits for prey to come within striking range. All three are noticeably less active than the snowy egret, which demonstrates the greatest assortment of strategies for finding food, and is therefore the most fun to watch.
The snowy egret is noted by many
authors as being the most energetic and innovative of this group
of waders. Like the others, it will often maintain its stately
pose for, what seems to us anyway, endless periods, gently swaying
and bobbing its head to estimate its prey's location. Ungainly,
catatonic poses from various perching spots may seem unendurable
to us, but of course benefit the bird by conserving energy while
it waits for dinner to be delivered. This also makes wading birds
appealing subjects for artists and photographers.
Egrets are most likely to be found feeding this way near creeks, docks, and culvert pipes where there is enough current to bring prey to them, and where there is little competition from other birds. A novice birder once asked me what advantage could it be to the egret to be white and stand out so dramatically in its surroundings. It's a good question unless you've viewed one from its prey's perspective. I once spent an afternoon snorkeling around a dock with my underwater camera, trying to get a close-up picture of a particularly tame egret that fished there. My biggest headache was trying to zero in on it from the water. Because the sky looks pale when viewed from below the water's surface, the motionless bird blended perfectly with its background - the sky. I am still hoping to capture a fish's eye view of an egret.
Egrets will use shadows to their advantage in several ways.
They often hunt under trees and at the edge of marshes where
there is shade and the surface glare, which interferes most with
fish-spotting, is less a problem. They will regularly orient
themselves so they are backlighted for this reason, a nuisance
photographers discover when they try to line up a stationary
bird for a portrait.
Birds also purposely create their
own shadows in the water. Apparently egrets can blend better
with their surroundings and look like a shrub to a fish by standing
on one leg. This also conserves body heat in cold water. The
word "pedigree," which is one's family tree, comes
from the French "pied de grue" - crane's foot. This
is sometimes represented artistically as a tree with exposed
surface roots or even a bird's foot in old ancestral diagrams.
Take a close look at the egret's legs and feet if you ever get
the chance. The tough skin really does make them look like tree
trunks, and undoubtedly fools fishes seeking a bit of shade for
cover too.
Sometimes birds will even hold their wings outstretched, as if they are trying to dry them. This is something known as canopy feeding and casts a larger, more realistic tree shadow. It is one of over 30 types of feeding behaviors that ornithologists have observed in waders. One tropical species, the black heron, takes the technique to the extreme by folding its wings completely over its head like an umbrella while it hunches down and waits for fishes.
Any fisherman will tell you that
movement scares fishes. So what advantage is it for an egret
to make sudden movements? When fishes are abundant in shallow
pools, or when other egrets and herons are present and there
is competition for food, the birds can change their strategy
and actively hunt for prey. Sometimes this means dashing gingerly
or hopping through the water stabbing here and there at suitable
targets. Other times the birds may spread their wings as they
run to stampede the fishes into shallow water. I've tried this
myself in the summer when I didn't have a net to catch bait,
and it really works. I've even gotten panicky killifishes to
jump right out of the water and onto the beach. Egrets are also
known to hover just above the water before descending suddenly
on their prey, one of four easily visualized behaviors classified
as aerial feeding hovering, dipping, and foot dragging and stirring
being the others.
When the water is cloudy and fishes are hard to see, egrets use yet another strategy, shuffling. This is where the bright yellow feet of the snowy are an advantage. Walking slowly through muddy pools and tidal creeks, egrets use their flashy footware to scare fishes towards the surface and into striking range. Witmer Stone (Bird Studies at Old Cape May) documents such behavior from an account of snowies at Troy Meadows (NJ) in 1929, when snowies were still relatively scarce because of the plumage hunting at the turn of the century. He wrote,"...The actions of one small white heron in particular attracted my attention. Instead of searching for its prey in the manner of the Little Blue Heron, it seemed to deliberately roil the water with raking foot motions and then seize the food that had been disturbed from the bottom...the bill was black except for a small yellow area at the base of the upper mandible. The bird was noticeably smaller than the Little Blue Herons in its company and when a blundering cow had put the herons to flight I detected yellow toes against a background of dark legs."
This is a more than adequate description of not only the behavior but the physical features that distinguish the snowy from its cousins.
Snowy egrets also poke their "golden slippers" daintily among underwater plants, apparently trying to lure fishes out of hiding, consciously "fishing" as humans do. They even bait-fish like people. I read a story about a snowy (emulating a green-backed heron in North Port, Florida) taking bread that residents throw to ducks in the pond and floating it along the shoreline as bait to attract minnows ... a bait-fishing heron and egret team.
When all else fails egrets still have one more trick that I don't often see, and since I've yet to find an ornithologist's description of it I will call it "gargling." To do it they extend their bodies out flat over the water to dip their bills halfway below the surface. By vibrating the bill rapidly they agitate the water with a sound like you make with the straw when you reach the bottom of an ice- filled cup of soda. It's weird, but it works, too. The fatal attraction that some fishes have for splashing water is thus exploited fully by the bird. How the egrets learned this is a mystery to me, but no surprise. Where there is a reliable food source there will always be some bird that has figured out a way to exploit it. That's why they fascinate me.
Lately, I've even heard tales
of egrets dangling shiny objects in the water with their bills
to attract fishes. Now, I have a lot of respect for these ingenious
creatures, but I'll believe that fish story only after I've seen
it for myself.
Something to think about:
- What is the advantage of similar creatures having different feeding strategies?
- What is the advantage of having "flashy" feet?
- What is the advantage of being a white-colored wader; especially when a juvenile like the little blue heron?