Notes on the behaviour of Caspian Terns on Lake Opinicon

Posted by: Mark Andrew Conboy

There are several species of water birds that do not breed at QUBS but visit us during and after the breeding season. These species include Double-crested Cormorant (Phalacrocorax auritus), Black-crowned Night-Heron (Nycticorax nycticorax), Ring-billed Gull

An adult Caspian Tern with a juvenile on the right and a Ring-billed Gull on the left. Caspian Terns typically usurp the highest perches on loafing sites such as Bird Rock on Lake Opinicon. Photo: Philina English. Click on picture to see a larger version.

(Larus delawarensis), Herring Gull (L. smithsonianus), Common Tern (Sterna hirundo) and Caspian Tern (S. caspia). All breed colonially, mainly on island in Lake Ontario and the St. Lawrence River and in many cases colonies are over 50 km from QUBS. Although a fair amount of information is available on the breeding activates of these species in the Kingston region we have virtually no information on their behaviour or ecology when they visit Lake Opinicon and other inland waters. Here I present some brief notes on Caspian Terns from August 2010. More observations of this and other species will help us understand the natural history of visiting water birds at QUBS.

Time of year: Caspian terns visit QUBS from mid August to mid September.

Abundance and occurrence: Up to 12 have been seen foraging over Lake Opinicon or lofting on small rocky islands, particularly Bird Rock off Joe’s Point. In addition to Lake Opinicon, small numbers of Caspian Terns have been recorded at other lakes in the region during the same time period: Newboro, Indian, Big Rideau and Loughborough.

Age classes: In general, adult birds seem to outnumber juveniles (young of the year) about three to one.

Care of young: Juveniles closely accompany foraging adults or wait on loafing rocks to be fed; in both cases they frequently beg.

Foraging: I recorded 9 foraging attempts by one adult around Bird Rock in the course of 30 min. Eight of those foraging attempts (near vertical plunge dives) were successful. On four of those successful hunts, the adult fed a begging juvenile. All prey items were fish but the species could not be identified.

Interspecific interactions: Caspian Terns commonly loaf on Bird Rock with Herring Gulls and Ring-billed Gulls. They frequently displace both gulls from the highest points on the rock.

Roosting: No sign of overnight roosting of terns or gulls was found with repeated evening checks of Bird Rock off Joe’s Point. Terns and gulls may roost on nearby fields.

The reasons why some water birds come inland from Lake Ontario and the St. Lawrence River to forage in smaller lakes while others remain on the larger water bodies is unclear. At least some Caspian Terns find it worth while to bring their young to Lake Opinicon. Is there an advantage for doing so? Do the same birds bring their young every year? How do birds that frequent inland water ways differ from birds that remain on big water? Further research into the behaviour and ecology of these visiting water bird species could be very interesting.

Female American redstart uses old red-eyed vireo nest

Posted by: Ann McKellar

Figure 1. Female American redstart building a nest. Photo: Carla Crossman

American redstarts (Setophaga ruticilla) are long-distance migratory warblers that typically begin arriving in the Opinicon region in early May. A female will pair with a male, inspect their shared territory, and then build a nest over several days. But as the breeding season progresses and nests continue to be depredated, a female can typically build new nests more quickly, sometimes managing to build an entire nest in as little as a day in late June and July. Redstart nests are usually built at the junction of three branches (also known as a crotch), often on the main trunk of a small tree or on skinnier branches of a larger tree. This type of structure allows support for the small cup nest, and a female will often be found placing her breast in various crotches before deciding where to build. When nest-building, female redstarts begin by laying down a base of spider web, and subsequently attach various materials, which can include bark strips, grasses, leaves, and lichens, to build up the walls of the nest. The final stage involves lining the inside of the cup, which is often done with feathers and mammal hairs.

On June 30, 2010, I observed a female American redstart laying down spider web in a crotch of a small sugar maple near Rock Lake

Figure 2. Female American redstart (tail visible) incubating on an old red-eyed vireo nest. Photo: Ann McKellar

Lane. I returned the next day, expecting to find the nest well on its way to completion. Instead, I found that the previous day’s nesting attempt had been abandoned, although the female still appeared to be building a nest somewhere nearby, as I saw her carrying nesting material. Puzzled, I continued to search for the female’s new nest for the next few days, without any luck. Finally, on July 6, I found the same female incubating three eggs in what appeared to be an old red-eyed vireo’s (Vireo olivaceus) nest. Red-eyed vireos construct their nests suspended from a fork or from two lateral twigs, and they are very different in appearance from the smaller, more secure-looking redstart nests. I was very surprised by this discovery, but after some research, I found that the use of old or deserted nests of other species, although not common, has been described previously in American redstarts. Verdi Burtch (1898) reported an American redstart female using an old red-eyed vireo’s nest that she had freshly lined, and Alfred Otto Gross noted in Bent (1953) three cases in which a red-eyed vireo’s nest was used by an American redstart female, one in which a yellow-throated vireo’s (Vireo flavifrons) nest was used, and one in which a nest started and abandoned by a yellow warbler (Dendroica petechia) was used.

Figure 3. Red-eyed vireo nest, used by an American redstart female. Photo: Ann McKellar

The redstart-vireo nest was ultimately depredated four days later, perhaps partly due to its conspicuousness. At this point I collected the nest in order to observe it more closely. The redstart had indeed used the foundation of a hanging red-eyed vireo nest, but had added some of her own lining material, which explains why I saw her with material on July 1. I suspect that the she was becoming desperate at such a late stage of the breeding season (two of her previous nests had already been depredated) and, giving up on starting a third nest from scratch, she decided to quickly re-line the already-constructed vireo nest.

References

1. Bent, A.C. 1953. Life histories of North American wood warblers. Dover Publishers: New York, New York, USA.
2. Burtch, V. 1898. Curious nesting of the American redstart. Auk 15: 332.

Bald eagles & coyotes

Posted by: Raleigh Robertson

On the morning of 3 February 2010,  at about 8 AM,  looking across the lake from our farm on Lake Opinicon, I spotted some activities near the far shore.  With my spotting scope, I discovered there were 2 Bald Eagles and 2 Ravens, feeding on a deer carcass.  It appeared to be a relatively fresh kill, since I could see the birds pulling on meat that wasn’t frozen, even though it had been minus 10 C overnight.  The Eagle plumage was quite distinctive, indicating one 2nd year, and one 3rd year.  About an hour later, there were 3 coyotes at the kill.  All were beautiful animals, in excellent pelage.  From watching urination events, I think one was male, one female, and the third, of unknown sex, was definitely subordinate – it consistently was submissive to the other two, and it often stayed off to the side, seeming to act like a sentinel.  The coyotes were eating, but also trying to haul the carcass over to the shoreline.  I later walked across the ice to check out the carcass, which was about 20 m from the far shore.  It was indeed fresh, meat along backbone still unfrozen, and it had been mostly consumed.  It was a small doe, possibly a yearling.  I think it was likely killed by coyotes during the night (the ice on the lake was quite bare, smooth and slippery,  following heavy rains a week ago, so a deer driven to the lake by coyotes would have very little traction), and then the pack of coyotes would have gorged on it, eating much of the meat.  Then at daylight, the scavenger birds had come in.  When watching the coyotes, I saw one taking a deer leg off into the woods, so the carcass was largely dismembered by 9 AM.  By about 10 AM, the coyotes were gone, and there was an adult Bald Eagle feeding at the carcass.   Then, by about 1 PM, there was a second year Bald Eagle at the carcass, and finally, at about 4 PM, there were 5 eagles and 2 ravens at the carcass.  The 5 eagles included 2 juveniles, one 2nd year, one 3rd year, and one uncertain, probably 2nd or 3rd year.

Interestingly, in later browsing the Bird Studies Canada website, and following their links to the eagle tracker –  based on the movements of Spirit, a bird tagged with a satellite transmitter in 2006, it is possible that the adult eagle I saw was this bird.  It’s location at the time seemed to be very much centred around Lake Opinicon.