Volunteer, Rick Lawrence and technician, Brittany Currier, making observations from the wetland edge.

This Thursday, I had the pleasure of going out in the field with volunteer, Rick Lawrence, and technician, Brittany Currier.  This was my first heron colony visit of the season and it was a rewarding one.  Despite post-holing through snow to get to the colony wetland, the day was relatively warm and more importantly, sunny!  When we reached the colony edge, I immediately noticed one adult great blue heron standing on one of the nests, and a second flying off in the background.

Volunteer, Rick Lawrence scanning the colony. One great blue heron was observed and is circled in red in this photo.

I quickly got a photo of the adult in the nest; it was a good thing I did because it soon flew off out of view.

Adult great blue heron at nest (had to zoom in a lot, here!).

This colony is one of our largest inland sites: we counted 42 old nests from last year.  Some survived the winter well and even looked as though they might have been fixed up a bit already, but there were also many that had considerably fallen apart.

We took our time at the colony edge, trying to get glimpses of other spring arrivals.  A pair of Canada geese flew in and landed on the still-frozen wetland.  Spring seems to be taking its time this year, but the birds are arriving on time and seem poised and ready for the nesting season.  Tree swallows, red-winged blackbirds, and common grackles could be heard or seen from various corners of the wetland.

Great horned owl in old heron nest.

The most interesting find of the day was a great horned owl occupying one of the heron nests from last year!  It was sitting low as if incubating eggs, thus we did’t notice it until we started looking at each nest individually.  The soft brown ear tufts waving in the wind above the nest’s rim gave it away.  This is the second time I have witnessed a great horned owl using a heron nest.  The last one I observed was on April 25, 2012 and the owl had at least 1 fuzzy chick at that time.  In that same nest tree were 4 active heron nests!  This time the herons have barely gotten started nesting, so it will be interesting to see if the herons mind the presence of a formidable predator.  Even if the owl’s eggs hatched yesterday, the young owlets would remain in the nest and be fed by the adults for at least 60 days, or well into June.  Needless to say, we will be watching this colony closely to see how the two species get along!

Photo by Doug Albert.

The great blue heron nesting season went by as quick as a flash this year.  Fall is when I collect all the HERON volunteers’ data and enter it into the database to get an idea of how the season went for herons (which I will blog about at a later date).  It is also a great time to visit colonies on the ground for several reasons: 1) I can usually get a fairly accurate nest count because the nests typically persist into the fall (and most often as long as the following spring); 2) the birds no longer occupy their colonies at this time of year, so I can get real close without causing any disturbance; and 3) there are no biting insects to contend with!

My colony of choice to visit this week was one that is 3.5 hours driving time from my office in Bangor.  Sometimes it is difficult to commit to a long day of driving for just one site, but this turned out to be well worth it.  The weather was absolutely perfect, the company was very pleasant, hospitable, and knowledgeable, and the site was quite unique as far as heron colonies go.  Below is a photo journal of the day’s visit.  Hope you enjoy the adventure…

My company for the day: HERON volunteer, Doug Albert.

Getting ready to launch.

Paddling upstream to the pond. This colony is in a flood plain setting on the edge of a pond. The easiest way to get there is to paddle up the outlet.

The water was quite low, which meant for lots of scooting over rocks. It also revealed these interesting rock mounds along the way. Many measured 2-3 ft in width and 1 ft in height. We had been talking about the rich Native American history in the area, so we had speculated they were some type of middens. A little more brain storming, searching on Google, and a consult with a fisheries expert back at the office uncovered the truth – they are Fallfish spawning mounds!

Fallfish (Semotilus corporalis) are a very large minnow that build communal spawning mounds that can be quite large. The adults average 12-17 inches in length, and construct these round nests by carrying stones in their mouths. They are primarily considered a bait fish by anglers, but are also eaten by piscivorous birds such as ospreys, eagles, and herons. Perhaps this is a main prey for the great blue herons nesting in the colony nearby?

What a peaceful setting.

A first glance at the colony before we round the bend into the pond. See the tiny black blobs in the center of the photo? Those are the nests. The nests are primarily in red maples, but we are peering through an oak stand. During the nesting season, the leaves of the hardwoods almost completely obscure the nests from view.

Where the pond’s outlet begins.

Rounding the bend and starting to get a better view.

Doug has his camera ready.

Getting an initial nest count. (Photo by Doug Albert)

Pausing to take it all in. (Photo by Doug Albert)

Ready to take a photo… or two…or more! (Photo by Doug Albert)

We counted 24 nests. There were 4 others to the left just outside of this photo that have blown down since June.

Paddling around a bit.

The approximate view from where we may set up a time-lapse camera to document disturbances. This colony failed mid-season, but the cause is thus far unknown.

Many thanks to Doug for monitoring this site the past 5 years, and for joining me for a great day on the water! (Photo by Doug Albert)

Adult great blue heron in flight over a nest with five young. Photo by Ron Logan.

In its fourth year, the Heron Observation Network of Maine continued to provide extremely useful information regarding Maine’s great blue heron breeding population.   In 2012, over 46 volunteers and biologists monitored 122 great blue heron colonies across the state.  We collectively made at least 170 observations from the ground, and 38 observations from the air.  Volunteers who tracked their time reported over 250 hours, which we can use as match for partial funding for our next big aerial survey effort in 2015.  THANK YOU to everyone involved!

While the HERON program is not designed to produce a reliable estimate of the great blue heron breeding population, or even a scientifically defendable trend, it does provide useful information that can help paint a picture of what might be occurring on a statewide basis.  Overall, the results still indicate a drop in the coastal breeding population and a potential drop in numbers at inland colonies as well.

One of the challenges with the HERON data is that it does not include every heron colony in the state nor does it reflect a random sample of the colonies.  The colonies surveyed are ones that willing volunteers and biologists can easily get to!  With limited time and resources, we will never be able to survey every historic and current colony in the state in one season.  We now have over 295 sites in our database that have hosted nesting great blue herons in recent or historic times.  New colonies are found each year, which indicates we are likely missing some, too.  Colonies may persist for decades, but they also may blink on and off, or splinter into several small colonies.  This dynamic nature of heron nesting ecology adds to the challenge of obtaining an accurate count of breeding pairs in any given year.

So, what does the monitoring data indicate?  Many of the colonies that have been “adopted” by volunteers have been surveyed in all of the last 4 years.  You might expect that those colonies would follow a similar trend to the entire statewide collection of colonies.  You also might expect that for sites that were monitored in only 1 or 2 of the last 4 years, the latest information for that site may still hold true.  Using the best available data that we have, we can show what we know and realize that the information has limitations.

Figure 1. Great blue heron activity observed at known colonies.

Figure 1 shows heron colony activity observations for each year.  There are certainly gaps in the data represented here.  The same colonies were not observed each year.  The 2010-2012 data includes new colonies found each of those years that had not been surveyed in years prior.  Even though some colonies may have become inactive, new colonies were also being added to the list.  Despite both additions and subtractions, the number of pairs appeared to decrease from 2009 to 2011 and then slightly increase again in 2012.  But, remember, there are many colonies that did not get looked at each of those years, so it is not a complete picture.

Figure 2. Great blue heron activity at known colonies, using most recent data to fill in gaps.

Figure 2 shows the same data as Figure 1, but I’ve added in the most recent data (collected 2009 or later) to 2010, 2011, and 2012 data.  This may give a more complete picture, and as you can see the line actually jumped a bit in 2010, but overall looks somewhat stable with an average of 1,070 nesting pairs each year.

Figure 3. Trend in # of nests at colonies observed at least twice between 2009 and 2012.

In addition to looking at the collective sum of colonies and pairs statewide, we can look at what’s happening within colonies.  Are the number of nesting pairs at each colony increasing, decreasing, or staying the same?  For any colony with 2 or more years of observations within the last 4 years, I determined the trend in nesting pairs.  There were 100 colonies for which I was able to do this, and 62 of those (62%) showed a decreasing trend in number of nesting pairs (Figure 3).  Even when sites are split into coastal and inland categories, the trend remains the same.  This is interesting to me because we have good data that shows a clear decline among coastal sites since the mid-1980s, but have yet to detect a trend for inland sites.  While this doesn’t definitively tell us there is a decline occurring at inland sites statewide, it may hint at it.

In 2012, we started tracking productivity at a subset of great blue heron colonies.  The best way to measure productivity is to know the number of eggs laid and the number of young that fledge for each nest.  However, because nests are high above the ground, we do not know how many eggs are laid by each pair, so instead we use the number of hatchlings as our starting parameter.  It is also difficult to document fledging of young because it happens over a relatively long period, and observers are not watching the colonies continuously.  Instead we use the number of young that reach an age close to fledging, or 5-8 weeks.  By tracking the status of individual nests and recording the number of hatchlings and number of young that survive to pre-fledging age (5-8 weeks old), we can get a measure of reproductive success by nest and for each colony.

Figure 4. Volunteers and biologists tracked productivity at individual nests within 18 colonies across the state in 2012.

Volunteers and biologists collected productivity data for 18 colonies in 2012 (Figure 4).  The average number of hatchlings seen in nests was 2.53 per nest; and the average number of young that reached pre-fledging age was 1.86 per nest.  The average success rate for colonies (% of young that made it to pre-fledging age) was 70.2%.  It is difficult to compare our rates to those found in the literature because methods vary subtly among studies.  However, this year’s effort was a start to understanding great blue heron productivity rates in Maine and will help us design meaningful studies in the future.  Over time, productivity measures can help determine the effects of land use changes, document effects of contaminants or diseases, and measure whether a population is reproducing well enough to sustain itself, given existing rates of survival.

So where do we go from here?  We obviously need more data!  My plan is to continue collecting data the way we’ve been doing so the past 4 years, but to also do a statewide aerial survey in 2015 that will “sample” the state in a manner that we can develop a population estimate.  The data collected via HERON will feed into the survey design and help us determine detectability of colonies.  For example, if we miss a “known” colony in 2015, then we can determine the percentage we missed and extrapolate from there.  My point is: we need to keep the data coming.   We need to know about all colonies, and we need more volunteers out on the ground observing colonies.

If you or someone you know may be interested in joining the Heron Observation Network or would like to report a colony, please contact Danielle D’Auria, 941-4478, [email protected].

Great blue heron nests are often found in snags located in beaver flowages. Photo by Michael Merchant.

Mention the great blue heron and most envision a large bird with long legs and neck knee-deep in water slowly stalking its prey. These wetland icons also rely on trees, both live and dead, for nesting. These magnificent birds build large platform stick nests 8-100 ft up in trees and nest in groups, or colonies. In Maine, colonies occur on coastal and freshwater islands, in beaver flowages, and in upland settings. Their nests are built in mature hardwoods and softwoods and can be in live, dead, or dying trees. Chances are, your property is potential nesting habitat for these prehistoric looking and sounding birds.

Great blue heron colonies may contain a few pairs to over a hundred, often with multiple nests occupying the same tree. Colony habitat preference is not completely understood, but they are most often located within 2.5 miles of several important feeding wetlands; in areas with few roads and little human disturbance; and within large contiguous forest stands. Nesting in colonies helps in terms of predator avoidance, but also makes them vulnerable to habitat loss. Impacts to the colony and even brief disturbance events near the colony can affect dozens of breeding pairs.

Maine’s great blue herons migrate south in winter to find ice-free feeding areas. As early as mid-March they begin to return to the state, and by mid-April many are setting up nests at colonies. Individuals tend to return to the same colony location each year. In Maine, some colonies have persisted for several decades.

Herons can also use trees with full canopies. Photo by Doug McMullin, Maine Coast heritage Trust.

During the nesting season (1 Apr – 15 Aug), the birds are extremely sensitive to disturbances caused by human intrusion, noise, and predators, and may even abandon a colony as a result. Their sensitivity varies in relation to the stage of breeding; the intensity, duration, and proximity of a new activity; woodland buffers or topography; and pre-existing uses on adjacent lands. The most sensitive times tend to be just before incubation (early May) and after the young are 4-6 weeks old (late June) and nearing fledging (late July).

The Maine Department of Inland Fisheries and Wildlife has developed preliminary guidelines to help protect and conserve great blue heron colonies. The main element of these guidelines is to minimize disturbance to the birds during the nesting season. To ensure this, we recommend a primary nesting buffer of approximately 660 ft around great blue heron nests, in which all human activity is avoided during the nesting period. Within approximately a quarter mile from all nests, it is also best to avoid major alterations to the landscape, such as land clearing, new road construction, and permanent structures.

Forest management can be a compatible land use for great blue herons. Timing considerations are critical; and fall or winter tree harvesting is preferred. To ensure minimal impacts, harvest prescriptions are best planned on site with a wildlife biologist. Management practices that maintain or improve the integrity of the overstory and provide for a continuing supply of mature trees favored for nesting are often rewarded with continued colony occupancy.

Great blue herons also nest in snags in wetlands; in fact most of Maine’s inland colonies occur in beaver flowages. A final consideration for conservation of great blue heron colonies is the protection of wetlands – both for nesting and foraging. Beaver flowages need beavers to maintain them; allow beavers to persist in these areas to some extent in order to create a stable water level regime. Landowners can protect wetlands and streams and shorelines of lakes and ponds by maintaining a minimum 75 ft no-cut zone, and adopting land use practices that protect water quality, limit erosion, and conserve native wildlife and vegetation.

If you find a great blue heron nest, please contact MDIFW at (207) 941-4466. Since 2009, we have tracked great blue heron colonies to better understand their statewide population status.

This is what the new HERON sticker looks like!

I am really excited to announce that the Heron Observation Network of Maine (HERON) is partnering with Burly Bird (a Maine-based conservation sticker company) to help raise funds for an important statewide aerial survey for nesting great blue herons scheduled for 2015!

Members of the public can support HERON in its efforts by purchasing a newly released UV-coated vinyl sticker that shows a black and white silhouette of a great blue heron.

The HERON sticker can be placed anywhere, including on car bumpers and windows, house windows to help prevent bird to glass collisions, water bottles, coffee mugs, laptops or bikes.

As you probably already know, HERON is a volunteer adopt-a-colony program started by the Maine Department of Inland Fisheries and Wildlife in 2009 in order to gain a better understanding of the great blue heron’s status within Maine.

The proceeds from the sticker will help fund the next aerial survey scheduled for 2015.

The great blue heron was designated as a Species of Special Concern in Maine in 2007 due to a decline in breeding pairs along the coast.  Little was known about the inland breeding population before 2009 when the Department ramped up its monitoring efforts by creating the Heron Observation Network.

Through HERON, volunteers across the state monitor known great blue heron colonies during the breeding season, collecting information that helps state biologists understand the species’ population trend and prioritize future conservation efforts.

In addition to the data collected by volunteers, it is important to periodically do a statewide aerial survey to find new heron colonies that may have recently popped up.

The Burly Bird HERON sticker is now available just in time for the holidays.  They can be purchased from the Burly Bird website  or through the Department’s online store.  They sell for $4 each with $3 going directly to fund the aerial survey.  Sticker sales will also help leverage federal funding through Maine’s State Wildlife Grant Program.

The HERON sticker is a great, inexpensive, conservation-minded gift for anyone with a love of the outdoors.  Get yours today!

Be sure to check out a short promotional video for the new HERON sticker on our YouTube channel, too.

Snowy egrets perched in apple trees.

This past May, I had the unique opportunity to assist National Audubon Society (NAS) with a wading bird census on Stratton Island in Saco Bay.  Part of NAS’s Phineas W. Sprague Memorial Sanctuary, this 23-acre island is located 1.5 miles south of Prout’s Neck and is home to an immense diversity of wading birds, waterfowl, seabirds, and songbirds, and is an important stopover for all the above during migration.

In fact, Stratton Island hosts the most diverse wading bird colony in Maine, and is the most northerly U.S. breeding location for a few of these species.  On the north side of the island, great and snowy egrets, black-crowned night-herons, little blue herons, and glossy ibis layer their nests in among the branches of choke cherry and apple trees.

Glossy ibis and little blue heron.

Despite this unique diversity of nesting wading birds, management and research efforts on the island primarily focus on the tern colony along the beaches.  The wading bird colony is essentially a “no entry” area with the exception of a 3-4 day period in May when the nests are censused.

The census is always around the third week of May, and coincides with a period just prior to peak hatch.  This timing maximizes the number of nests with a complete clutch of eggs and minimizes the number of sensitive nestlings that are disturbed.  The census is conducted in the morning for a maximum of 2.5 hours.  This prevents exposing eggs and newly hatched nestlings to the hot afternoon sun, and allows the disturbance to be contained to just a portion of the day enabling the adults to focus on provisioning their young the rest of the day.

Stratton Island’s wading bird colony, as seen from a boat.

As we move through the colony, we locate nests, number them the metal tags, and identify them based on nest structure and contents.  Many nests can be checked by simply peering over the nest edge, but a good portion are well above our heads and require a mirror pole (a pole with a mirror attached on one end) to see into them.

It is not easy work.  The branches of the trees and shrubs are interwoven producing an almost impenetrable barrier between the observer and the nests.   Not to mention the invasive bittersweet entangling many of the trees adds to the mess.  The branches are all covered with guano (bird feces), which inevitably gets all over us.  We also need to tiptoe around common eider nests that are well hidden in the ground cover of raspberry bushes or stinging nettles.  The eiders usually flush before we get there, but I’d hate to step on those eggs they have worked so hard to protect from real predators (compared to us clumsy humans).

Surveyors using a mirror pole to see into a high nest.

Once we do get a good view of a nest, we count the eggs and nestlings and decide on species.  This is also not an easy task.  They all have greenish-blue eggs that are elliptical or sub-elliptical in shape, and their nests are all made of sticks, twigs and sometimes finer material.  So, how do we do it?  It is a combination of egg size, shape and color, nestlings (if they are present), and the nesting materials.  We do have one sophisticated tool for determining the eggs by species: a piece of cardboard with a hole in it!  If an egg passes through it, it most likely does NOT belong to a black-crowned night-heron or a great egret.  Then we go through a series of comparisons and essentially a process of elimination. 

Nest in amongst the tree branch tangle.

In the end, we can do fairly well EXCEPT for distinguishing snowy egret and little blue heron – their eggs are identical.  A high count of adult little blue herons seen during the census is noted; half of that number is the likely minimum number of little blue heron nests that year.

I don’t know what this year’s final tallies were, but the yearly average is a total of 255 nests!  For example, in 2009, 272 nests were counted:

Below are additional photos of some nests, eggs, and nestlings.  See if you can get the gist of what we are keying in on…

Comparing eggs: snowy egret on left and black-crowned night-heron on right (I think!).

Black-crowned night-heron nest with eggs. Eggs are more “squat” than snowy and great egret eggs.

Snowy egret nestling. Photo by Robby Lambert.

Snowy egret nest with eggs. Eggs are evenly oval. Great egret nests are also made of sticks, but generally are larger; eggs are slightly larger as well. These eggs look white due to direct sunlight, but they are really a greenish-blue. Photo by Robby Lambert.

Glossy ibis nest with eggs. Egg on right is a bit atypical. Ibis eggs are a deeper blue and tend to be more teardrop shaped. Nest has more elaborate lining with finer materials than all the other wader nests.

Glossy ibis nestlings and 1 unhatched egg. Note the dark feathers and pink bill with black stripes.

Glossy ibis nestlings and 1 unhatched egg. Photo by Robby Lambert.

Great egret nestling. Photo by Robby Lambert.

This work is supported by state revenues from the Loon Conservation Plate and Chickadee Checkoff Funds.

How do they keep cool on those 90+ degree days?  Like humans, birds rely on evaporative cooling to release heat; however, birds do not have sweat glands like you and me.  Instead, they lose heat through their respiratory tract.  Some birds do this by panting, but others, including herons, do so by “gular flutter”.  Gular flutter is a rapid vibration of the upper throat and thin floor of the mouth.  By opening their mouths wide and rapidly flapping the thin gular membranes of the throat, they expose a large featherless area to moving air.  To see what gular flutter looks like, click on the link below to a web album containing 2 short videos:

Gular Flutter Videos

Herons may also change their posture to keep cool.  The “sunbathing” posture or “delta-wing” is sometimes assumed to aid in cooling the bird itself as well as to help shade its nest contents (eggs or nestlings).  Often sunbathing is accompanied by gular flutter.  The sunbathing posture I witnessed below was seen in mid-May on a day that was not noticeably hot (at least to me, but I was shaded by a blind).  This adult most likely had eggs or newly hatched young in the nest, but it doesn’t appear that the sunbathing posture is serving to shade any nest contents here.  The adult is actually facing into the sun.  Perhaps this is one of many reasons that led to this nest’s failure?  It was inactive only 1 week later.

Adult great blue heron “sunbathing”.

Last Wednesday I took to the field to check out a great blue heron colony that I have only seen once during an aerial survey in 2009.  Since then, a volunteer has been monitoring the colony on the ground.  I finally made personal contact with the landowners this year and made a date to meet them and take a walk through the woods to the beaver flowage that housed the snags that held the heron nests. 

As we approached the wetland, we quieted ourselves knowing that our presence could easily disturb the nesting herons.  We ducked in and out of brush and young trees and snuck our way stealthily towards an opening at the water’s edge.

Adult great blue herons during incubation.

We saw one heron fly up from its nest, circle around above the wetland, then quickly return to its nest.  This wetland is full of dead standing trees, or snags, but most of them are little spindly things not strong enough to support the large stick nests that herons build.  Intermixed with the spindly spires, stood several trees on which several herons chose to build their nests.  

I began to scan the trees looking for nests, counting as I went, and cataloguing which nests were active (or had herons sitting in them), and which were not.  Several trees held one nest each, but there were a few trees that were tall and stout enough, with just the right horizontal limbs to support multiple nests.  One tree had two nests, one had four, and one had five!  

 By late April and early May, most great blue herons inMainehave laid their eggs and have started incubating them.  Incubating herons can be extremely difficult to detect with the naked eye and sometimes even with binoculars or a scope.  They have this amazing ability to fold their long legs, neck, and wings and tuck themselves down so far into their nest that from a human’s perspective they are practically undetectable.  Undetectable – except for the bright orange bill and the white and black stripes on top of the head.  This is what I look for, and what I saw last Wednesday. 

Osprey nest.

Out of 16 nests in this wetland, 11 were occupied by herons, all incubating.  Three nests were inconclusive – no sign of an adult heron.  The largest nest on the far end of the wetland was occupied by a pair of osprey, which is not an uncommon occurrence.  And the last nest?  Well, this is where it gets interesting.

 Remember the tree with 5 nests?  As I scanned that tree from top to bottom, checking each nest as I worked my way down, here’s what I saw: a nest with an incubating heron, a vacant nest, a nest with an adult great horned owl and a fuzzy owlet, a nest with an incubating heron, and another nest with an incubating heron.  Wait a minute!  An adult great horned owl AND a fuzzy owlet?  That owl is practically nesting in its kitchen!

From top to bottom: incubating heron, vacant nest, adult great horned owl and a fuzzy owlet (of course there's a twig in the way), incubating heron, incubating heron.

Great horned owls are potential predators of great blue herons.  But, as I stood at the edge of the wetland looking on in wonder, there was no sense of predator-prey strife here.  The herons were sitting low in their nests in incubating posture as you would expect and the owl just stood by in its nest with its young next to it.  No signs of stress at all. 

 My bird brain says that owls and herons shouldn’t nest next to each other, and especially not in the same tree, at least not for the herons’ sake.  You would think that the owl might choose to nest near the herons, but not vice versa.  However, it is the owl who arrived and chose its nest first this year.  Great horned owls use stick nests built by other birds such as hawks, ravens, and herons.  The owl began nesting in February when the herons were somewhere well south ofMaine.  The herons likely arrived back in late March or early April.  Despite the owl taking up residency in the herons’ colony, the herons chose to nest here again.  And for some reason unbeknownst to me, they even chose to nest in the same tree as the owl.  Talk about tempting fate! 

Perhaps there is something about this wetland that makes it a prime site for nesting herons; something that overrides the risk of nesting with a potential predator.  I have heard it suggested that the owls may serve to keep mammalian predators away, or that the herons may serve to keep crows away (have you seen how ruthless crows can be to owls?).  Great horned owls are known as potential predators of great blue herons.  Those who follow the Cornell heron webcam know that a great horned owl attacked the incubating adults several times this year already.  I do know of a heron colony that one year hosted herons and the next year only a great horned owl and no herons; so in that case the herons did not choose to nest near the owls – their tie to that colony did not override the possibility of becoming the owls’ dinner.

 Despite the many possible reasons why these birds are nesting within a few feet of each other, I can’t wait to find out how the season progresses.  I will keep you posted with my observations.

Old heron nest occupied by adult great horned owl and its fuzzy owlet.