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

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. 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. 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.

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.

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.

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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.

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Molly Meserve is a graduate student at the University of New England.

Hello, my name is Molly Meserve and I am a graduate student at the University of New England in Biddeford, ME. Along with all of you I will be closely observing the fascinating behavior of Maine’s Great Blue Herons this summer. As a Maine native I am particularly interested in this work because the Great Blue Heron has been a constant in my life here in Maine. My master’s thesis focuses on the following question: Do prey delivery rates and total foraging times of Great Blue Herons in coastal and inland colonies differ and how may these factors affect chick survival? With the help of Danielle D’Auria and some wonderful HERON volunteers I have been able to visit a few of the Great Blue Heron colonies in the State. Two of those colonies have been chosen as the main focus of my study; the inland colony is located in Hollis, ME and the coastal colony is in Brunswick, ME. I will be out in the field from April 1st until about mid-August observing from ground blinds that I have set up in each of the sites mentioned above. While in the field I will be focusing on gathering accurate numbers of adults, chicks (their approximate ages), and nestlings along with prey delivery rates and time spent foraging for each nest observed.

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Logan Labree, Dalton McCaughlin and Rachel Bates measure and record the diameter of a great blue heron nest tree while Skip Walsh (in background) searches for another nest.

On a brisk fall afternoon after most students have headed home from Sebasticook Valley Middle School, 10 students remain.  They each don a hunter orange cap supplied by the school and head outside.  Today’s meeting of the Maine Outdoors Club is a unique one.  They have two guests: Brad Allen and I, both biologists with the Maine Department of Inland Fisheries and Wildlife (MDIF&W).

Though it is hunting season, the students are not going to learn about hunting laws or ethics.  Instead, they will assist with monitoring a great blue heron colony located literally in their back yard, right on school property.

The school district’s great blue heron colony was originally reported to MDIFW by local residents in 2009.  The initial ground visit by biologists last April revealed only six nests, but the breeding season had just begun and the colony was likely not yet fully occupied.  An aerial survey of the site in late June revealed an estimated 30 nests, most containing nestlings.

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Remains found beneath heron nests. Clockwise from top left: egg shells and membranes, crayfish claw and fish backbone, fused rear vertebrae and pelvis (from 3 different aged herons), heron feathers, heron skull and mandible, leg and wing bones.

Did you know that you can learn a lot by what is on the ground at the base of a heron’s nest tree?  A heron nest is only so big, so there’s no room for food remains and other forms of heron “trash”.  Herons simply just pitch it all over the edge.  Out of sight, out of mind, I guess.  Light blue eggshells with some membranes in tact indicate a successful hatch; but you may also find remains of young herons that met their premature demise by falling to the ground.  Adult feathers that were molted are often found.  You might find out that crayfish is a favorite food of the family above.  This disposal area for the herons nesting above can really be a treasure trove to a researcher trying to find out how dam removal affects the birds that use a river.

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