Home » Cerulean Warbler
Category Archives: Cerulean Warbler
After a prolonged and complicated change of address it felt good to stroll through Frontenac woods again! The field season has begun. Our plans are full, as usual, but our focus will shift from the more specific pursuits of recent years back to the bigger picture. Point counts, point counts and more point counts are in order. In addition to widespread surveying there will also be demographic monitoring (MAPS and nest searching/atlassing) and a role in a collaborative project with Bird Studies Canada and Canadian Wildlife Service to examine the current population status of Cerulean Warblers in Ontario. The Frontenac Arch is THE hotspot for Cerulean Warblers in Canada. About a half dozen were heard singing this morning amongst the emerging foliage of the forest canopy.
I still marvel at the number of species with provincially or nationally critical connections to the Frontenac Arch region. The Gray Ratsnake (Pantherophis spiloides) is a perfect example. This is Ontario’s largest snake, growing up to 2.5 meters in length. This species has retracted considerably from its historical range but they seem to be holding on in the Arch – a familiar trend. I found this meter-long individual warming itself on the road this morning. After a bit of resistance from it I was able to move it off the road to safety. Unfortunately, collisions with vehicles are one of its main threats.
This video was recorded yesterday while revisiting the site where a Louisiana Waterthrush nest was found on May 26, 2010. The stream at this site is flowing with so much vigor that the two waterfalls severely limit the audibility of my playback system. Despite this I was able to locate a territorial male at the south end of the stream complex in a low valley sandwiched between two small ridges. I promptly ended playback as soon as the male responded and watched him for about ten minutes or so as he moved back and forth from the stream to higher perches. At one point he moved higher toward the canopy and was instantly chased off by a bill snapping small passerine, which turned out to be a female Cerulean Warbler (Dendroica cerulea). I followed the female for several minutes and hit an ornithological jackpot of sorts when she flew to a nest located on a horizontal branch of a large Sugar Maple (Acer saccharum), about 15m above the ground.
Cerulean Warblers build their nests high in the upper canopy of deciduous forests that have mature trees, little or no understorey and small gaps or breaks in canopy closure. These characteristics make their nests quite difficult to find and even harder to inspect and monitor! In this case I was able to get a decent view of the nest from either of the two ridges, which put me roughly 15 feet closer to the crown of the large trees growing in the valley. Even with this advantage I still had to zoom to 39x to get a low quality recording. Gotta thank the 749 mosquitoes for all the shakiness. I will definitely be returning to this site (with a tripod!) to monitor both of these important breeders in the next several weeks. Frontenac Provincial Park is one of the most significant protected areas for Canada’s population of Cerulean Warblers now listed as an Endangered species by COSEWIC.
Back to the waterthrush surveys. Things have picked up a bit since my last post but it seems that 2011 will be marked as a down year for breeding Louisiana Waterthrushes in this region. I have not been successful at several reliable sites despite as many as four repeat visits. A review of historical records show some evidence of a downward trend occurring since the first half of the last decade. Despite an apparent population decrease coinciding with the initiation of our study in 2010 it is critical to monitor the sites through the good times and the bad times. Interestingly, the high number of unoccupied sites found this year has only buoyed my interest in the study going forward. Also, the 2011 season is not over yet as surveys at five more sites are yet to be completed and I do have four active sites to keep tabs on.
The Point Count is a standard method for gathering data on the relative abundance of breeding birds. This method typically involves a 3, 5 or 10 minute count of all birds detected from a fixed position and is conducted year-after-year from the exact same spot. Annual replicates of point count surveys enable the calculation of population trends and can also infer correlations of temporal changes in relative abundance to specific habitats and many other parameters dictated by survey design. For the Frontenac Breeding Birds project, we will be completing 80 off-road point count stations within Frontenac Provincial Park as well as 120 roadside counts along secondary and tertiary road systems in the study area. This is a big undertaking but will provide a sound baseline assessment of the avian communities in the area. At least for now our point counts will be focused on terrestrial habitats, primarily of the forested kind.
I emerged from the house at dawn on June 8th to begin the first morning of point counts in mature deciduous forest habitat in the park. I heard a Winter Wren singing mightily from the opposite shore of our dock and wondered if I might have a chance to investigate later in the day after the surveys were done. I was about to enter some of the oldest forests in the region and didn’t have any time for dawdling so I carried on to the first station after a short boat trip across Kingsford Lake.
These forests are quite diverse with tree species but the main representatives are Red and White Oak, White Ash and Sugar Maple. The light diffusing through the canopy was quite spectacular and I was pleased to write down a singing male Cerulean Warbler at MH1, the first station of the day! Ceruleans are quintessential canopy dwellers, rarely descending to heights that would afford even a decent glimpse, although they do occur in less mature forests at Queen’s Biological Station.
This is one of the grandparent trees in the forest, easily a century old White Ash that pierced through the upper canopy. My jets hat was used to give a better sense of scale of this monster!
This is a view straight up to the canopy along the trunk of the ash and the Ceruleans like to hang out up near the top somewhere. Fortunately, I’ve been finding that their buzzy songs carry a decent distance through the forest and they are frequent songsters, even well into mid-afternoon.
This particular point count route was about 4 kilometres long in total with twelve stations spaced evenly by 330 metres. The route carried me nearly the full length of Kingsford Lake to the north end of the park and Devil Lake. There was much more than just birds to look at during the trip including this abandoned mica mine, which was established in 1844 and terminated in 1949. The mine shaft was fenced off and all that remained of the operation were piles of mica shards and a heap of old equipment and furniture as seen in the photo below. Mica is abundant in the area, glowing in the soil and exposed rock on sunny days.
The undulating landscape of ridges and valleys is a hallmark of the Frontenac Arch where the Canadian Shield rears up dramatically at its furthest position south. The valleys often contain ephemeral pools and wetlands, which create ideal growing conditions for these ferns that were over a metre and a half tall. Northern Waterthrushes thrive in these areas of the park.
Back to the birds. After completing the first route through mature forest on the 8th, today I finished up the first of three routes to be conducted in younger hardwood forest of the park. An obvious highlight of the two survey routes was the abundance of Cerulean Warblers detected. This little wet clearing in a relatively young hardwood stand contained three males that sang from the confines of their respective territories at the edge of the clearing.
This is a photo of one of my survey forms from this morning, which records no less than three counter-singing Cerulean Warblers! The inner circle has a 50 metre radius and the outer extends from 50-75 metres. This grid is used to keep track of who is where while you are working as it can become quite confusing when there are a lot of birds in your immediate area. The hashmarked lines connecting CERW and SOSP indicate countersinging birds, which helps to confirm that individuals aren’t being double-counted. Birds with small dots were detected in the first three minutes and those with stars and triangles were recorded between 3-5 and 5-10 respectively. There were twelve species within 75 metres at this particular station, including a Yellow-billed Cuckoo (YBCU) and a Scarlet Tanager (SCTA) among the Ceruleans (CERW), American Redstarts (AMRE) and Red-eyed Vireos (REVI). Also present were Northern Flicker (NOFL), American Robin (AMRO), Song Sparrow (SOSP), Great Crested Flycatcher (GCFL), Chipping Sparrow (CHSP) and White-breasted Nuthatch (WBNU).
The first day of point counts finished off nicely with a Louisiana Waterthrush near Crab Lake at the last count and in the last minute! In all a total of 14 Cerulean Warblers were detected along the route through mature deciduous forest. Another 15 were recorded this morning in younger hardwood forests near Birch Lake to the south of Kingsford for a total of 29 singing males in two mornings of point count surveys in Frontenac Provincial Park! The 24 surveys completed so far are at best a slice of what is there and I still have two more routes of twelve counts each in the younger hardwood forests.
Lastly, after walking back the four kilometres from Crab Lake on Monday, I checked in on that singing Winter Wren I’d heard singing about seven hours before. After about 60 minutes of quietly watching the male and female in their territory, I was able to locate their nest underneath this mossy old stump. It was pitch black under there and I had to basically lie down in the swamp with my flashlight and pocket mirror to find what is effectively a hidden hole in the ceiling of the stump about the size of a two dollar coin! The nest contains three very small chicks and with any luck you will notice the tips of their bills in the photo below.
(Singing Cerulean Warbler-ZHEE ZHEE ZIZIZIZIZI zzzeeet)
Of the three MAPS stations we’re establishing for the Frontenac Breeding Birds project, I’ve definitely had the most difficulty finalizing a layout for the Maplewood Bog station to the north of Frontenac Provincial Park. This particular site seemed to have the most uniformly structured forest and the least number of readily identifiable edges. It was however, the closest thing to pure deciduous forest of the three, which presented our best opportunity to sample species typical of this forest type. My last visit on May 14th, just ten days ago, gave me a bit more confidence that a viable MAPS station could be conducted there but I still had some lingering doubts.
I returned to MABO (station codename) this morning with the hope that I might find some lovely rock outcrops, forest clearings or wetlands that I’d missed on previous visits and also that some new species had arrived since mid-May. Today was my day as I found both! The most notable change since the last visit was the rather sudden appearance of Cerulean Warblers at the site (second only to a mass irruption of Mosquitos!). I hadn’t encountered them previously at MABO but they have been numerous along Canoe Lake Road this spring. In Ron Weir’s latest edition of Birds of the Kingston Region, he makes note of a high count of 25 singing males along Canoe Lake Road on May 15, 1979. Cerulean Warblers seem to have a tendancy to aggregate into colonies, although the reasons for this habit are unclear. Each MAPS station is 20 hectares, inside of which standardized misnetting of breeding birds occurs within an 8 hectare plot. I was delighted to find a total of five singing males within the banding area itself, none of which were audible from the nearby road where the site is accessed. Some of these vocal males may be unmated bachelors but I was able to confirm two pairs and found some evidence of nesting. Ceruleans were located in younger portions of the woodland with an uneven canopy and open understory and seemed to be favouring spots with mature oak sp. protruding through the canopy. The Cerulean Warbler is one of the most heavily declining bird species in North America and is a species of Special Concern in Canada and Ontario.
In addition to the parade of Cerulean Warblers, I also found a great abundance of other deciduous species, the most conspicuous of which were Veery, American Redstart, Red-eyed Vireo and Scarlet Tanager. Other birds of note were Yellow-throated Vireo, Barred Owl, Wilson’s Snipe, Swamp Sparrow, Black-throated Blue Warbler and Magnolia Warbler. The foliage was markedly further along today than my last visit and this was a great help in finalizing the layout of the MAPS station. I didn’t have much time for nest searching but I was very happy to find a Scarlet Tanager nest about 10 feet above the ground at the edge of a blanket bog!
With the layout for MABO now having been properly visualized, we are set to begin site prep next week in advance of our first visit to all three sites in the first week of June. The MAPS work will operate in tandem with an extensive network of on and off-road point count stations throughout the 15,000 hectare study area. An intensive nest-monitoring effort will also commence during the first of June. It will be an eventful and probably very tiring two months of fieldwork but we are in an excellent position to deliver this exciting new initiative. I wonder how many Cerulean Warblers can be found in 15,000 hectares of forest in the northern Frontenac Arch?