Sunday, 30 July 2017

Variation in size in Barn Swallow nestlings

     The second broods of Barn Swallows (Hirundo rustica) are now well advanced and we have banded the birds from numerous nests already.
     Recently, we extracted six nestlings from a nest and noted a significant size difference between the birds. Three were distinctly bigger than the other three, feather development was more advanced and it appeared that two different hatch dates were involved.  Judging that the smaller birds were too small to band, we banded only the three larger birds. Unfortunately we did not weigh them, being more concerned with getting the birds back to the nest as quickly as possible.I should add here that we have adopted the practice of returning the young birds back to the nest individually, as soon as we have processed them, rather than waiting until all the nestlings have been dealt with. In this fashion, they seem to find their place in the nest more readily and align themselves with each other in a way that does not threaten any of them being pushed out of the nest. (See picture below of the nest when all occupants have been returned).



     I mused to Kevin at the time that egg dumping might have been a factor in this size discrepancy, although I was unaware of this practice which is common among other families (waterfowl, for example) being noted in Barn Swallows. 
     Today we encountered this phenomenon again. The pictures below are not of great quality, but you can clearly see that the bird at the bottom left is substantially smaller than its siblings, with feather development less advanced.




     In fact, here are the weights of the five nestlings: 9.3 grams, 18.7 grams, 17.3 grams, 19.0 grams, 16.7 grams. The slight variation in the bigger four is easily explained by normal factors in nestling development, such as some youngster being more aggressive and getting a higher proportion of feedings from the adults, but the fifth bird is clearly in a different category. Furthermore, it was healthy, squirming around in my hand when I returned it to the nest, gaping right away for food - and it was promptly fed by one of its parents. There was nothing to indicate anything other than a robust youngster, less advanced than the other nest occupants, but entirely commensurate with the progression we have observed in other birds.
     Here is information gleaned from the literature which might shed some light on this condition.
     From Swallows & Martins (1989), Angela Turner and Chris Rose:
     Barn Swallows are nearly always monogamous, but there have been records of males pairing with two females  and, in colonies, males often copulate with females other than their own mate.
     Thus, it is possible that a second male may have inseminated a female after she has been incubating for several days which then causes her to lay an egg which hatches later than the initial clutch.
    From Handbook of the Birds of the World (2004), Volume 9, Josep del Hoyo, Andrew Elliott, David Christie, editors.
     Socially monogamous, occasionally polygynous, extra-pair paternity common, c. a third of nestlings in European studies, 22% in Canada (Ontario). Egg dumping by conspecifics occurs (3% in Spanish study, with nest-owner male sometimes the father.)
     Again, it is possible then, that a male copulated with a female other than his mate, and that female deposited her egg in the nest while the host female was absent.
     If anyone has anything to add to this account we would very much welcome your comments.
     As a total aside, you can observe the amount of horsehair attached to the nestlings when we retrieve them from the nest. This material seems to be a bit of a mixed blessing. It is readily available and seems to be favoured by the swallows for nest construction but it can sometimes be lethal. We found one young bird hanging from a nest totally entangled in horsehair - and dead. On several occasions we have been able to disentangle birds whose movement was seriously restricted and doubtless would have starved to death, unable to move freely and obtain food.
     
     

Saturday, 29 July 2017

A Visit to Hespeler Mill Pond, Cambridge, ON

26 July 2017

     Recently Miriam and I were in the vicinity of Hespeler Mill Pond and dropped down there to see whether we could locate a Red-necked Phalarope (Phalaropus lobatus), a great rarity, which had been reported a few days earlier. Fortunately, it was still present, albeit far out, but we had no difficulty finding it, and I had my scope with me so good looks were assured. 
     Eastern Cottontail (Sylvilagus floridanus) appears to have had a prolific breeding season and we were greeted by a friendly member of the clan.



     Hespeler Mill pond is not in fact a pond, but a spot in the Speed River where it widens considerably, just downstream from former textile mills, long since dormant as the entire, once dominant, textile industry in Canada has succumbed to competition from the Far East.




     It is always a good location for migratory shorebirds, but this year the water level seems particularly favourable and there are many plovers and sandpipers present covering a range of species - with more still to come.
     When our regular group had met the day before, the Red-necked Phalarope was mentioned, and it became clear that none of the others had ever seen one, and some had never visited Hespeler Mill Pond, so we agreed to meet there at 08:30 the following morning to try our luck.
     As it turned out the phalarope had not been seen the previous day, and we, along with other birders and photographers present, were unable to locate it. Doubtless this errant individual has moved on.
     This news did not dim our spirits one bit for there was a panoply of avian activity spread before us, with much to see, to study and to excite our attention.
     A Double-crested Cormorant (Phalacrocoax auritus) moved along at a leisurely pace right in front of us.




     A prominent stump attracted the attention of everyone; a Midland Painted Turtle (Chrysemys picta marginata) and a Juvenile Spotted Sandpiper (Actitis macularia) seemed to be "hanging out" together. 



     As this remarkable series of pictures taken by Franc reveals, the Spotted Sandpiper was intent on capturing the flies around and on the log, and the presence of the turtle was entirely incidental.








     I can't help but think that Franc's pictures get a little better each week and I am pleased and grateful that he agrees so readily to share them with us. Nothing makes Franc happier than getting a good shot, but he is always respectful of his subject and never does anything untoward to cause stress or undue disturbance.
     An American Mink (Mustela vison), lightening fast both on land and in the water, posed only briefly for a portrait.




    There were many, many Lesser Yellowlegs (Tringa flavipes) present, with lots of space and ample feeding area for all, yet this duo seemed more intent on squabbling over one little patch of water than going about the business of fattening up for the long migration ahead.






     Greater Yellowlegs (Tringa melanoleuca) was less numerous than Lesser Yellowlegs, but this individual was still in breeding plumage.



     And this one is an exemplar of grace and beauty as it coursed over the water.



     CaspianTerns (Hydroprogne caspia) were plunge diving for fish, with a high success rate, shaking the water off their plumage as they emerged from the water.




     An adult seemed to be delivering food to an offspring while at the same time imparting a lesson that it was high time for it to start procuring its own food. It would transfer the fish to the young bird's mouth and promptly snatch it back again.






     Hespeler Mill Pond is well known as a fall roosting area for Great Egret (Ardea alba) and already their numbers are starting to build. Most disperse after roosting for the night, but a couple were still present when we arrived.




     There were about fifteen Great Blue Herons (Ardea herodias) in attendance, including
this individual flying in tandem with a Kildeer (Charadrius vociferus).



     Juvenile birds were proving that they were getting along well with the serious business of
life.




    Everyone enjoyed their visit and I suspect that it will not be long before we make another stop to see what new species have arrived.

All bird species: Canada Goose, Mute Swan, Wood Duck, Mallard, Great Blue Heron, Great Egret, Kildeer, Least Sandpiper, Pectoral Sandpiper, Semipalmated Sandpiper, Spotted Sandpiper, Solitary Sandpiper, Greater Yellowlegs, Lesser Yellowlegs, Ring-billed Gull, Caspian Tern, Common Tern, Belted Kingfisher, Northern Rough-winged Swallow, Black-capped Chickadee, Common Yellowthroat, Red-winged Blackbird, House Sparrow. Total: 23 species.

Thursday, 27 July 2017

Tuesday Rambles with David - rare Charitable Research Reserve, Cambridge, ON

25 July 2017

     It was as fine a summer's morning as anyone could devise when all eight members of our regular group met at 08:30 in the parking lot near the slit barn at rare for our weekly outing. 


     It was the kind of day when it was simply good to be outside; it mattered little what one might see, the sheer exuberance of rambling in bright sunshine with warm breezes was enough. But, there were many things to be observed. And (modestly, I might say) the fact of being part of the finest gang of eight ever assembled did nothing to dilute the pleasure.


       This is the time of year when butterflies abound. Common Woodnymph (Cercyonis pegala) was exactly that - common.


     It seems to have been a relatively good year for Monarch (Danaus plexippus) compared with recent years, when this species has been scarce indeed, and we can only hope that their numbers are rebounding.



     The population here in southern Ontario is part of the cohort that makes a legendary migration to Michoacan in Central Mexico, a journey and a destination discovered by Canadian entomologist, Fred Urquhart. The butterflies generally arrive on schedule each year on El dia de los Muertos, the Day of the Dead. Fittingly, la mariposa monarca is believed by the residents of the area to harbour the souls of departed loved ones returning for their annual visit.
     A Northern Crescent  (Phyciodes coctya) seems pedestrian by comparison; it bears no responsibility for taking lost souls back home.



     A Wild Indigo Duskywing (Erynnis baptisiae) is the fourth butterfly that we were able to photograph, although other species were seen.


     Perhaps Francine is on a quest for them here.


     Cedar Waxwings (Bombycilla cedrorum) were quite common, with many juveniles in evidence.


     Many were seen flycatching across the Grand River, but equally they were involved in gathering the plentiful berries that ensure that in July in Ontario, the living is easy!



     The plight of pollinators across the world is well know to everyone, so it is always reassuring to see them, such as this bee on a teasel, at work.


     Japanese Beetles (Popilla japonica), beautiful they may be, are not quite as welcome; these alien invaders represent a serious threat to native vegetation.



     Judy heard the sneezy fitz-bew song of the Willow Flycatcher and Franc took this lovely photograph.


     We observed a couple of male Ruby-throated Hummingbirds (Archilocus colubris) defending their territories.



     This one zoomed out at some perceived threat.



     These tiny creatures are fearless in defence of what they believe is theirs and will attack without hesitation, no matter the size of the intruder.
     This male House Finch (Haemorhous mexicanus) looked especially fit and handsome; no doubt it has fathered a brood this season.



     Or perhaps its nest was parasitized by a Brown-headed Cowbird (Molothrus ater) such as this female seen here.



     The undoubted star of the morning was a family of Western Osprey (Pandion haliaetus).
This pair has successfully raised three young which are on the verge of fledging. This bears testament not only to the diligence of the parents, but also to the biomass of fish in the Grand River watershed, supporting not only Ospreys but a variety of other fish-eating birds, and mammals, to say nothing of fishers of the Homo sapiens persuasion.





     Everyone was either taking pictures or was focused on the enchanting spectacle in front of us.



     I think the rest of these pictures speak for themselves.









     I would imagine that these young birds are mere days away from fledging, when their parents will teach them how to fish for themselves, before beginning the long and dangerous migration south. Many of them will not make it, but those that do have an excellent chance to return here to raise their own families.
     Every Tuesday ramble has its own charm and rewards. Today was no exception. And we planned a bonus walk for the following day. You can read about that soon, so be sure to check in over the next few days. Thanks for visiting!

All bird species: Mallard, Turkey Vulture, Western Osprey, Ring-billed Gull, Mourning Dove, Chimney Swift, Ruby-throated Hummingbird, Belted Kingfisher, Hairy Woodpecker, Northern Flicker, Willow Flycatcher, Eastern Kingbird, Barn Swallow, American Robin, Grey Catbird, Cedar Waxwing, Common Yellowthroat, Song Sparrow, Northern Cardinal, Rose-breasted Grosbeak, Red-winged Blackbird, Common Grackle, Brown-headed Cowbird, Baltimore Oriole, House Finch, American Goldfinch, House Finch. Total: 27 species.