Fieldwork has kicked into full gear as the action-packed month of June is just a week away. Our Louisiana Waterthrush surveys are nearing completion for the 2012 season. Soon I will be racking up the mileage while scouring the barrens for Prairie Warblers and other goodies in the southeast section of the park. It’s such a wonderful contrast to transition from damp mature forests to the hot and dry expanses of bedrock, poverty grass and junipers. Yesterday I found this Barred Owl in a wooded swamp about 40m from where my truck was parked on Salmon Lake Road. Barred Owls are easily the most common owl species in the area. Great Horned Owls are comparatively rare in the hardwood forests but are found with some regularity in mature mixed coniferous zones. Owl populations would be an excellent subject FBS in the future.
Louisiana Waterthrushes have been very scarce this spring, even more so than last year. The species was recorded at seven sites in 2010, our first year, but only evident at two sites so far in 2012. Fortunately, they are paired and probably nesting at the two sites. The steep sided stream corridors seem so empty without their voices.
Many species are well into their nesting cycles. While observing the Barred Owl I tracked a female Black-throated Green Warbler, which had just finished bathing in the swamp. After a bit of preening and some flitting it plunked itself into a fork at the main trunk of a young Yellow Birch. Raising binoculars to the spot revealed a surprisingly deep and bulky nest. The earliest nest record for this species in Ontario is June 5 so a nest with eggs on May 24 is quite early. This particular record is also somewhat unusual in its location in a deciduous tree species within purely deciduous forest. In Frontenac Provincial Park the Black-throated Green is more typically found in woodland with tall Eastern White Pine and/or Eastern Hemlock. However, a quick search of our point count data revealed that they are present, albeit in low numbers, within hardwood stands as well.
Below is a photo of habitat suitable for Golden-winged Warblers. This was taken just southwest of Westport, ON where there are many small, family-run farms with low-intensity agricultural practices. The presence of dense shrub cover at edges of property lines provides appropriate conditions for Golden-wings, which were designated as Threatened by COSEWIC in 2006. A total of six male Golden-winged Warblers were located yesterday morning with relatively little effort. The Frontenac Arch and the southern shield ecotone are important regions for the protection of this species. In these areas, the rugged terrain and shallow till have been effective deterrents to large scale/intensive agriculture, so far…..
Land O’ Lakes indeed! Frontenac Provincial Park lies at the southern tip of the great Canadian Shield with its astounding proliferation of lakes, wetlands and rivers. The map clipping above provides a glimpse of the difficult terrain here and also the number and distribution of lakes. The landscape is rich and beautiful but often very harsh too. The park has an impressive history – of miners, farmers and loggers who endured extreme hardship eking out a life here. The route I took this morning passes by abandoned homesteads and mines as well as the old log roll way at Hardwood Bay on Devil Lake. A century ago the land was mostly cleared and the air would have been filled with the sounds of men and women working the land. Decades of regeneration later, the area provides mature oaks, maples and hickories for troubled bird species, Cerulean Warblers and Red-headed Woodpeckers.
Very pleased to find that the Red-headed Woodpeckers have returned! Hopefully this means that they were successful rearing young last summer. I watched the pair fending off Common Grackles from a nest site and also observed the pair copulate twice. I’ll make a point to return to locate the nest later on in the season and hopefully get some footage of the young being fed at the nest.
I sought out this fantastic forest swamp for our ongoing project to inventory Louisiana Waterthrush habitat in the study area. This was a site that had not been visited before. I took the liberty of naming it Devil’s Swamp in my records. Northern Waterthrushes were present but no Louisianas today. This would be a high priority site for future monitoring, especially in years when the population is healthier in the region. Once again, Louisiana Waterthrushes are present this year at only a few sites in the region but we are also finding a dearth of unmated “wanderers”.
Prairie Warbler (Dendroica discolor)
Nidiologicals – Peck and James (1987) and Nolan,V.,Jr., E.D.Ketterson, and C.A.Buerkle (1999)
Habitat – Dry, early successional shrubland habitats ranging from pine plantations, dunes, mangroves, barrens, clearcuts and abandoned fields.
Microhabitat – Cup nest usually well concealed in upper crotches of shrub
Spring arrival – Early to mid May (Ontario)
Average nest height – .6m-.9m
Nest builder – Female only
Average # of broods/season – 1-2 (variable with latitude and local conditions)
Average egg laying date – 8 June-19 June (Ontario)
Average clutch size – 3-5 eggs
Incubation period – Average 12 days
Egg colour – White to greenish white with variable brown spots, usually wreathed at larger end.
Incubation – Female only
Brown-headed Cowbird host – Yes
The Prairie Warbler is a rare but regular breeding species in Ontario. It is estimated that about 300 pairs occur annually in the province, although there is some evidence of recent decline due to habitat succession of granitic rock barrens along the edge of the southern shield region. We’ve been surveying and studying Prairies in Frontenac Provincial Park for the last two years and have found a small but apparently healthy population in open barrens with scattered young trees and pockets of dense shrub cover. The above photo was taken within the core breeding area, which is about 20 hectares in size and characterized by low tree cover, exposed rock, dense ground vegetation and thick patches of vibernum sp. and junipers. Most Prairie Warbler territories here are associated with sloped shoreline edges of beaver ponds and lakes, which may be a function of denser shrub growth occurring in lower lying areas.
This photo shows a typical nest site along a rocky slope where Downy Arrowwood (Viburnum rafinesqueanum) proliferates. Four nests have been found so far this summer and all but one were positioned near the top of a viburnum at heights between .7m-1.3m. All four nests have been located along slopes ranging from gentle to sharp and with no apparent preference for aspect.
Prairie Warbler nests resemble those of the Yellow Warbler (Dendroica petechia), a fairly close relative but less common inhabitant of the rock barrens. Prairie Warblers favour hot and dry environments while Yellow Warblers tend to occupy wetter shrubland habitats with a more flexible tolerance for shade/canopy closure. This nest with four eggs was discovered on June 26 when a female was flushed from a small clump of viburnum. When incubating female Prairie Warblers notoriously sit tight and only flush when very closely approached.
This is a shot of the same nest within the shrub. Prior to nest searching this season I was anticipating that Ground Juniper (Juniperus communis) would be the most common host plant for nests but it seems that the viburnums are more abundant and probably preferred here. They are a stout and sturdy shrub with woody main stems and branches, while the leaf cover provides excellent concealment and weather shielding from all sides. The only non-viburnum nest was located in a lonicera sp. that grew within a large clump of Downy Arrowwood.
Two of the four nests were found by patiently following adults carrying beakfulls of plump, green caterpillars. One of our colour banded males (nickname “Whitey”) led me to this nest with five young. Thanks are due to Julie Zickefoose for helping Seabrooke and I age these nestlings. These little prairielets were identified as being 5-6 days old and only a few days away from leaving the nest.
This female was photographed incubating on June 26. When I returned five days later I was disappointed to find that the nest had failed, probably due to predation. Common Grackles, Blue Jays and snakes would be the most likely nest predators in the barrens. I’ve twice found Ribbon Snakes (Thamnophis sauritus) above the ground within shrubs here. On the upside it appeared that the female, or perhaps a different female, was preparing to rebuild within the territory or perhaps even reuse the failed nest. The attached male (also colour banded) was singing vigorously while the female inspected forks of shrubs and called softly. On two occasions she was observed for five-minute periods shaping and touching up the failed nest. Hopefully the second attempt will fair better than the first!
May 30th was probably one of my top 5 most enjoyable days of fieldwork since Frontenac Bird Studies began. The weather was perfect, the biting insects were oddly subdued and I could scarcely walk 100m before needing to georeference some exciting critter. I saw many butterflies, moths, snakes and plants of note but the centerpiece was a wetland that Steve Gillis and I explored during our first biothon in July 2010. Below are two panoramic views of the swamp from the south and east respectively (click to enlarge).
The wetland is fairly large by frontenac standards, about 9 acres in total area. It is distinctive in having a small raised island of live trees (mostly pine) surrounded by a flooded lowland dotted with snags and fallen trees. Surrounding the wetland is mid-successional oak-maple forest with scattered mature trees, an open understorey and with ground cover dominated by grass. The area was absolutely teeming with cavity nesters – Northern Flickers, Hairy Woodpeckers, Yellow-bellied Sapsuckers, Great Crested Flycatchers and White-breasted Nuthatches mostly. Apparently the area is so irresistible to Common Grackles that they were also nesting in cavities 10-15m above the water – an unusual choice for them (1.8% of nests reported to Ontario Nest Records Scheme n=2652).
At the far north end of the swamp were two large platform nesting species – Osprey (1 nest) and Great Blue Heron (3 nests). These and the all the cavity dwellers put on quite a show! The bordering woodland was also active with Cerulean Warblers, Red-shouldered Hawks, Yellow-throated Vireos and a single Olive-sided Flycatcher being the most noteworthy. The Olive-sided is the first I’ve seen in the region and probably a migrant, although suitable is available north of the park closer to highway 7. You can hear it singing in the video clip above (quick-three-beers) along with the odd Cerulean Warbler.
The birding at this site in July of last year was less memorable, probably due to the fact that it was during a mid-afternoon in July. However we did spot a pair of Red-headed Woodpeckers that day (Melanerpes erythrocephalus) – a rapidly declining species (Threatened status) in Ontario. It turns out that the species has been retracting from many parts of its range but heavily in Eastern Ontario. Our observation was the second of only two documented breeding records for Frontenac Provincial Park, although breeding evidence was not officially obtained in 2010. I bookmarked this as a target for 2011 and am pleased to report that it took me less than 30 minutes to confirm an active nest site this past Monday!
Their active behaviour and brilliant high contrast of their plumage made them easy to track and observe within the open wetland. An adult called repeatedly from the west end of the swamp but rarely approached the nest (the male?). The other adult, presumed to be the female, made frequent trips to a cavity near the top of a 14m tall snag close to the southeast shoreline. The video at the beginning of this post highlights some of the activity at the nest site, which seemed to be exclusively short incubation sessions as no excavation or food carrying were noted. We will return to this site again in the next week or two to check on its progress.
The Red-headed Woodpecker is an extraordinary bird for many reasons. This post is already running long so I’ll have to return to this topic at a later date to highlight its unique ecology and relationship with human settlement. Below are two instructive breeding evidence maps from the Ontario Breeding Bird Atlas, which visualize the widespread decline of this species in Southern Ontario. For further intormation, The Birds of North America account (subscription needed) is essential reading for this species but the Cornell account hits some key points too.
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.