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The HERON Blog has moved and will no longer be posting to this website. Don’t worry, we’ve moved all the old content to the new site as well.  Please update your bookmarks to: http://www.maine.gov/wordpress/ifwheron/

First Field Visit a Rewarding One

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.

2013 Heron Observation Network Photos from the Field

To celebrate the Heron Observation Network’s fifth year, I put together a collection of Photos from the Field, taken by myself, co-workers, and some very talented HERON volunteers.  Many THANKS to all the HERON volunteers who monitored colonies, and to the landowners that allowed access.  Here’s to another exciting year ahead of us!  Happy 2014!

Fall Colony Visit

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…

Painting a Picture from the 2012 Results

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, danielle.dauria@maine.gov.

Forestry and Herons Can and Do Mix

The following article was originally written for the October 2012 issue of “SWOAM News”, the newsletter of the Small Woodland Owners Association of Maine: 

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.

Sale of New HERON Sticker Will Fuel 2015 Aerial Survey

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.

National Audubon’s Island Jewel is Maine’s Most Diverse Heronry

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.

How Herons Handle the Heat

We’ve had some hot sultry days this summer, and if you were smart you retreated to a shady spot or went for a swim at a nearby pond.  But what about all those great blue heron nestlings that were sitting in their nests 20-100 feet up in a  tree, often in full sun?  Sure, their nest tree may be surrounded by water if it is a snag in a beaver flowage, but that water is completely inaccessible to a nestling who takes around 80 days to learn how to fly. 

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”.

Herons Return to Colony Despite Nesting Owls

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.