The Ecology of
Maryland’s Yellow Crowned Night Heron: We’re All in This Together
Human Values Network
Presentation October 30, 2011
Mike Stahl
Why do I want to tell you about Yellow Crowned Night Herons? They are elegant representatives of the Heron family of which there are many species. They can tell us a lot about the health of their habitat; if they are present it suggests that pollutants in the streams are lessened because the crayfish they prey on are abundant; the crayfish are abundant because the soil and the sea weeds that sustain them are healthy. The term healthy is used liberally-healthy enough is really the case. They are also very easy to do field studies on from the bridge on Wyman Park and from the shore of the Jones Falls below.
(39°19.272” N; 076°37.814”W
for those who care).
The Yellow-Crowned represents several aspects of natural life that means a lot to me and to humans in general. They adapt very well to a changing environment. They can be salt water avians or live in fresh water environs. They can live in deep woods or in an urban area as my story attests. It is their business to stay alive and to generate future herons; they need to do this in a shrinking habitat.
Adapting in nature describes one form of symbiosis. I say as often as I can “That we are all in this together, the flora, the fauna and us humans”. Every organism from sentient ones to bacteria relies in some way on each other. We can witness the Yellow Crowned Night Heron as part of food chain as I will briefly describe later.
Becoming better adapted to a current ecological habitat or learning to dwell in new or changed environments is one of the key concepts of adaptation. In our current world there is no stasis and all living things are in a constant flux learning to adapt to the environment they find themselves in.
Life goes on for a species essentially due to survival and reproduction and that is the largest part of my point about the Yellow Crown. This bird is in a continual (albeit quite slow) process of moving northward. This is a condition many birds find themselves in and it is not too foolish a leap to imagine that warming waters and air play a role in that. They also find themselves living in the city. In the example that I present, the fact that they are so visible and prey to rock throwing young boys, changing conditions of the waters and the fields below auto emissions and more, testifies to their knack for survival. The basis of my story revolves around their giving birth and there you have it, survival and reproduction.
In broader terms-ones that we cannot witness change, the bird has evolved features that make them adapt to the streams and rivers that they populate. They have long and very strong beaks that allow them grab the crustaceans that make up the bulk of their diet. Their long legs and their ability to stand perfectly still for extended periods allow them a sort of invisibility. When they do grab their sustenance, they do it with lightening swiftness. They also use bait such as worms or flies that they lay on the water top in order to lure their dinner to the surface when that is the best way to dine. Of course the sexy plumage that dangles from the male’s forehead and drifts about in the wind is the pheromone exciter that brings the ladies of spring to their mates.
Yellow Crowned Night Herons essentially live by eating so that they can mate and generate, well…more generations. It is a pretty easy life. They re-use nests by simply bolstering the ones from last year so that they can produce a new brood. There are no maids, mechanics, professors or rabbis amongst the birds; it is a life pretty much made up of eating and reproducing and resting. They do migrate south but not so much.
There was one thing I discovered in my research only after witnessing it in real life. First year maters often make nests that are too weak. In 2010 one nest broke from its branches and fell into the Jones Falls meaning that no new generations came form that mating. It was sad as the hatchlings had broken out of their eggs and as little fuzzy sentient beings met their fate after a few short days. This year the same nest was reinforced and the two year old parents (mom anyway) were able to see their offspring off to fledge.
So the Yellow Crown adapts structural traits in order to eat, mate and protect itself. They have behavioral traits that are adapted for their hunting and eating. They have physiological adaptations that allow them to live in the ecological niche that they find themselves in.
Stalking the banks of rivers and streams both salinic and not, the Yellow Crowned Night Heron is in search one of the many invertebrae used for sustenance. Its appetite is voracious and searching for food can last the better part of its day. It has a long powerful bill adapted for the crunching necessary to crack the shell of a crab or crayfish.
The Yellow Crowned Night Heron is a member of Ardeidae order of Ciconiiformes Ardeadae and is specifically Nyctanassa violacea. Group name is “A siege of Herons”. I have been following these and other herons primarily in Robert E. Lee Park for many years but it was in 2010 that I became aware of the rookery a few miles south near the Stieff Silver Building.
The first Yellow Crowned Night Heron recorded in Maryland was in 1921 which coincides with a broader northward expansion of the species. This fact is misleading because no one tracked this species prior to the 1921 census. The bird has a natural habitat here and undoubtedly has been here since prehistoric times. It is a growing species and several studies have been conducted to examine its local population. Here are some sample results of studies taken: Mating pairs in 1977 numbered 55 in 10 colonies; versus 2003 with 476 mating pairs in 57 colonies.
In Sand Dunes and Salt Marshes published in 1913, Charles Wendell Townsend does not distinguish between the species of night herons suggesting that even as late as 100 years ago, the Yellow Crowned was not considered its own species but was lumped together with the similar Black Crowned Night Heron.
They are migratory as our winters are too harsh for them. They do not travel particularly far as migrations go and spend time in Florida and along the South Carolina coast as well as in Baja Peninsula and into Central America.
In terms of their viability as a species in this rapidly changing environment it is pretty sound at this time. The species is stable with known threats but is not in peril. Any decline is due to predation and interspecific competition along with disappearing wetlands. All this means that like other fauna, their populations and distributions are monitored but they are relatively abundant and not close to being threatened at this time.
The Yellow Crowned is found mainly east of the Mississippi and south of the Mason Dixon Line. We first see them in Maryland towards the end of March as they return to nesting rookeries to reinforce existing nests and to build new ones. At my vantage point of Wyman Park Road, they mainly are renewing old nests though I will be monitoring this coming March to see if new ones arise. I did not think to start this field study that early in the season in 2011 but next spring it will be different. During the winter I can count the existing nests which I currently believe to be seven in number.
In this bird’s second year it is ready for some amour. While they breed as monogamous with the male very much a player in the chick raising, he puts on a dazzling display for affection. This of course means fetching the sticks that will become the nest. The male also grows some long plumes from the supercillium (forehead) that sway in the wind and are proof of his wealth and heritage. This activity begins in April with nests built about 25 feet above a stream. The nest building duties are left to the female with the male’s job being to gather the right materials. He is the one who goes to Lowe’s so to speak. The nests are pretty massive as this is a pretty large bird.
Here is a breeding male.
During breeding season, the yellow-crowned night heron will build a nest of sticks and twigs measuring two or three feet across. This nest is generally a substantial platform that can be found on the ground, or low in a tree, by a body of water. The female will lay three to five eggs that are a pale bluish green in color. The eggs are about twice the size of the eggs you might crack in your kitchen prior to breakfast. They brood one time per year. The female stays on them for close to 100% of the time for the incubation and is fed by her mate. During incubation the male stays very close to the nest except when hunting which suggests protection.
The eggs hatch in about three weeks, and both parents care for the chicks feeding them regurgitated food. The chicks fledge when they are about 25 days old. They have to be able to maintain body temperature, at two weeks (mid to late June) they can perch on a branch. An observer can watch the development of the hatchlings which only takes a few weeks to go from the broken egg to a flying and feeding young bird. They grow very quickly and are essentially adult size about 60 days after birth (or hatch I suppose). The chicks are active and eager to fledge. They stalk the limbs regularly and flex and flap their wings. They grow rapidly but their wings develop slower than their bodies. One can see the thinness of their wing structure (from my vantage point on the bridge) several days before they can fly.
They have one brood a year with 2-7 eggs more commonly 3-5. Both parents share incubation. Hatching is asynchronous and the birds emerge with variant sizes. Like all birds the loudest shrieker gets the most attention from the parents and it happens that some die from malnutrition. Siblicide is also common. While fledging they eat regurgitated food from either of their parents.
Once hatched it emerges with the strong beak. Like all birds it is covered with down. At this point it is about the size of a Robin.
These young ones are about 10 days old and have doubled in size. They are beginning to stretch and stalk all in preparation of flying which means leaving home.
Now a week or ten days later the young one is ready to search for their dinner. It takes several days of wing stretching before they can fly. When they first begin the stretch you can see that their wings have not fully developed. Initially they do their hunting nearby either of their parents but they learn how and what to eat very rapidly and are on their own very quickly once fully fledged.
Upon leaving the nest it is only a matter of a few days before they start life on their own. They are full sized and have the evolutionary talents that come with their breed. Like all young they are susceptible to the hazards of youth. Inexperience can cause them trouble but as a species the Yellow Crown is not at a crisis so they tend to be successful during their first year.
Once they are about a year old their full coloration is
present. The male and female look pretty much the same. During the mating
season the male grows very long plumes in its brow and they flow about the
wind-that is about the only way to distinguish the sexes. As adults they stand about two feet high and
weigh around one and a half pounds. (I find that hard to believe given their
size). The yellow-crowned night heron is
generally found in shallow backwaters and wetland areas.
This night heron
is a short stocky bird about 24 inches in length with a wingspan of a little
under four feet. It has long yellow to orange legs, red eyes, a black bill and
a short neck. The adults are a soft blue-gray, blackish on wings and tail, with
a creamy white crown accented by a black face and white cheek patch. During
breeding season, adults have a yellow plume of feathers on their head. The
young, appearing in mid-June, are uniformly brown streaked.
Its name may
imply nocturnal (active only at dark), but the Yellow-crowned night heron is
active both day and night. Even with its daytime activities, the handsome
bird’s slow movement, along with its shy behavior makes it a difficult bird to
spot.
Their prey normally
consists of fish, frogs, grasshoppers, and occasionally snakes, but its primary
diet is crustaceans (crayfish). It is also not uncommon to see one prey upon a
small turtle since it has a unique stomach acid to help digest the shell.
Finally they
fledge and migrate leaving only the remains of a sturdy nest.
Addenda One-The Heron
Diary
March 28:
It is migration time. In February I came home to something like 50 Robins in my
yard, eating the dried berries that were fruit last summer. Within a few days I
came home to about as many Grackles. The latter was reminiscent of Hitchcock’s The Birds as these starkly
black birds hovered everywhere.
On my morning walk of about a mile from the Light Rail stop to work is still in
the dark (owing to the recent change to Daylight Savings Time) and as I head
east I can hear the Peregrines screaming above. One morning shortly after
daylight became real, I saw two of them on the roof of
the old Community College building on Lombard Street. They will become more
obvious for the next couple of months.
My big news has to do with a life bird. One morning about 3 weeks ago I found a
nearly all black small duck in the inner harbor during one of my walks. I did
not know what it was but do keep a field guide in my office and determined that
it was a Black Scoter. Several days later I saw another one (or perhaps the
same one a second time). Within a week I saw them everywhere including at one
sighting, ten of them at once. I did some research and understand that they
summer in the Hudson Bay so I expect they will be leaving soon. It is nice to
see a visitor. It is also nice that they are good posers so I have some photos.
Last fall on a beautiful day, many Terns came by the harbor for one day. I am
not sure if they were Least Terns or Common Terns but they were Terns and they
crashed into the water with a boom in search of victuals. No camera that day
though.
Down near the Stieff Building above the Jones Falls,
the Yellow Crowned Night Herons are back building nests and getting ready to
brood. There are no leaves yet so the view is clear. Here is an early shot of
some of them. I saw five perching within view of the bridge.
In the backyard I have a dearth of birds on most days. The nuthatches that
wintered here are gone as are the Juncos (of course 10 minutes after writing
that I saw two of them bouncing around the porch eating the spilled seeds of a
feeder). Today it is pretty boring with only the standard Cardinals and Song
Sparrows hanging around. There are crows above (yesterday I looked up at all
the caws and saw what appeared to be a Crow Tree as
so many perched on it). They looked like fruit.
I still do my volunteer work with Lights
Out Baltimore and that began a few weeks ago. We walk a four mile downtown
path around particular buildings in search of compromised birds. They are in
their state mostly because they have crashed into buildings while migrating
confusedly through a downtown area. We are apt to come upon some exotic birds
because it was not their intention to stop here. Sometimes we can save them
thanks to the volunteers who are trained to restore as much of them as
possible. Unfortunately we still have about 75 carcasses to donate to science
every season.
If I learned anything during the last 12 months is that if you look every day,
you will see something new.
May 1:
Once or twice a week now, I go to the Jones Falls bridge
near Druid Hill Park to keep fresh on the Yellow Crowned Night Herons that nest
under that bridge. I am learning more about their nesting habits and
photographing them routinely. Currently there are five nests that can still be
seen from the bridge. Four on the south side and one on the
north. You can look into the one on the south side and on April 30 there
were two eggs visible. Since it is easy to spot herons sitting on the south
side nests which were constructed prior to the south side one it is hard to
imagine that they are not egg filled as well. You just cannot see into the
nests to confirm the existence of eggs.
The adults continue as couples at least through the mating season and rear the
young together so there are a lot of these herons hanging around the branches
or on the nests themselves.
The Peregrines are back on the downtown buildings and I often hear them and
less so see them. It is clear that years after the DDT ban, Peregrines are
rebounding as a species. Curiously it seems that the last few generations are
making urban America and Canada their habitat. I suppose that is fine though I
am not convinced of it. There are plenty of Rock Doves and other birds
available for their sustenance but are those birds, with their urban diet of french fries and other scraps,
providing the nutrition either for their own survival or that of their
predators? It seems like it wouldn't be but I do not know.
I'll keep updating on the success of the herons.
This morning I walked the reservoir at Druid Hill Park and saw approximately 1
billion Red Wing Black Birds. They are not too afraid of humans and will perch
very close allowing a really good view of them. In the water itself I saw one
Bufflehead and one Barrows Goldeneye neither of which
I expected to see there.
Stay tuned.
May 8, 2011
In my weekly (or more when possible) visit to the
Yellow Crowned rookery I chose to walk under the nests to see what new
discoveries I might find.
From the vantage point of the bridge the nests are getting more obscured by the
leaves that are in abundance and view blocking. From below I actually found 6
nests rather than the four reported earlier. Judging from the nesting habits I
would think that eggs lay in each of them. I can only see eggs on the north
side of the bridge.
Last year the one on the north side of the bridge disappeared shortly after the
eggs hatched. I thought (and reported) that young boys successfully destroyed
it but calmer and more knowledgeable heads prevailed and told me that there
were plenty of natural events that could have occurred to sink the nest. One
such notion as I have learned from research, suggested that first nests are
often too fragile and ill made to endure the time necessary to render chicks
free to live their lives. I have also learned that nests get reinforced even
after chicks hatch, by the more experienced parents. I am seeing that in action
this year.
Let’s see what happens. I know a bit more than last year and will learn more
this year as I watch as the late spring unravels.
May 15, 2011
It’s pretty quiet at the 6 nest rookery over the Jones
Falls near Druid Hill Park. It would appear that all nests have eggs as there
was a bird on each one at 7:30 in the morning. It is all quiet to the human
observer that is. There is a lot of gestation going on.
May 22, 2011
Finally, a beautiful spring like weekend morning.
Today I saw my first hatchlings in two of the nests north of the bridge. Here
is an early photo.I'll keep you posted.
June 5, 2011
The herons are hatching now. Here is a photo of a
mother and young. From below I count 6 nests. From the bridge I can only see
three since the leaves are out and are broad.
June 19, 2011
I was out of town last week but got out to Stieff
early this morning. This time with a friend in tow who not only enjoyed the
hatchlings but also saw her first Baltimore Oriole
which are regular visitors to the area. The hatchlings appear healthy and the
nests intact.
With lush foliage one can only see four nests from the bridge but climbing down
into the park below one can see seven nests.
After a good long walk we hiked up to Druid Hill Park and I was exposed to a
path that was brand new to me and quite lush and beautiful. We ran into another
friend and three of us walked for a few miles. When we got to the reservoir we
found a pair of Cedar Waxwings only a few feet away and at eye level. They
flitted around some and we could watch them for quite awhile. In my mind they
are the most beautiful bird that Maryland has to offer and it was a first for
my friends. I do not see them so often to ever get bored with them.
June 25, 2011
As usual I go to the park to check the new borns out
pretty early in the morning. Its cooler and there is less traffic. For a while
the dense foliage obscured the view from the bridge but the young ones are
growing fast. They are not ready to fly as their wings are not developed
enough. That at least is how I surmise it. They do a lot of wing stretching and
there is a lot of gap in the feathers at this point.
From underneath the nests there is a lot more to view. It is not possible (at
least with my technology) to get a good photo as the trees canopy the area into
a nice cool shady spot. Here is a photo of a few of the young ones taken this
morning.
July 2, 2011
From my vantage point on the bridge overlooking The
Jones Falls, I can see four nests, obscured as they are by dense foliage. In
two of the nests I can no longer see any activity. I have to guess that the new
birds have fledged and are out their learning to eat
real food by watching their parents along nearby streams.
In the other two nests the hatchlings remain but are actively touring the large
branches. They do some sunning and stretching their wings.
July 17, 2011
I was camping at Point lookout last weekend and therefore missed the final
fledgling of the season. The youngest threesome were
nowhere to be seen on this visit...nor were any others. It was a good spring,
none of the hatchlings died. They all looked healthy and were maturing as one
would expect.
I'm not sure where they head to but since a few miles north is a popular Yellow
Crowned Night Heron summer resort. It is Robert Lee Park where I have visited
many times but not during the last 19 months as it has been closed. It was
there on the banks of the 150 year old man made falls that represent the headwaters
of the Jones Falls that I have seen copious numbers of Yellow Crowns both
mature and otherwise. I have also seen both in the stream that runs through the
Mount Washington neighborhood of Baltimore but none were there when I looked
early Sunday morning.
I am determined to keep a routine vigilance of the rookery despite its
desertion. When this blog is complete it will be about a year and a half
because I am interested in the early mating season towards the end of winter.
I'll keep you posted.
September 4, 2011
There is not much to report. I took my daughter to the
site and we could only see a few of the nests as the leaves are still abundant.
The birds of course are long gone. I'll check back in a month to see if enough
leaves have fallen to view the many nests from the bridge. I'll let you know.
October 16, 2011
Of course the birds are long gone but I wanted to spend a few moments of this fine day to see if enough leaves have fallen to be able to count the nests from the bridge. They had not but I wanted a photo of one of them for a discussion group.
Addenda Two- Taxon
recognized by IUCN:
Animalia
Chordata
Aves
Ciconiiformes
Ardeidae
Nyctanassa
Nyctanassa violacea
Ciconiiformes N., Order of chiefly tropical marsh-dwelling fish-eating wading birds with long legs and bills and (except for flamingos) unwebbed feet: herons; storks; spoonbills; flamingos; ibises
Ardeidae N., Herons; egrets; night herons; bitterns
Nyctanassa N., American night herons
1. Williams, B, Brinker, D, Watts, B, and Erwin, R 2007 The Status of Colonial nesting wading bird populations within the Chesapeake Bay and coastal barrier island lagoon system. Waterbirds Special Publication #1 82-92
2. http://epa.gov/climate-change/effects/coastal/slrmaps.html
3. http://www.nebirdmonitor.org
4. http://www.allaboutbirds.org/guide/Yellow-crowned_Night-Heron/lifehistory
5. National Audubon Society The Sibley Guide to Bird Life and Behavior. New York, Alfred A. Knopf, 2001 ISBN 0-679-45123-4
6. Erlich, P, Dobkin, D, Wheye, D The Birder’s Handbook. New York, Simon and Schuster, 1988 ISBN 0-671-65989-8
7. Alderer, J (ed) National Geographic’s Complete Guide to Birds of North America. 2006 ISBN 0-7922-4175-4
8. Lender, M, Salt Marsh Diary. New York, St. Martin’s Press 2011, ISBN 978-0-312-65601-0
9. http://en.wikipedia.org/wiki/Yellow-crowned_Night_heron
10. http://respectfulbirding.blogspot.com/2011/03/spring-time-update.html
11. Townsend, C Sand Dunes and Salt Marshes. 1913 Dodo Press ISBN 978-1-4099-8473-8