The return of summer!?

The temperatures in the past week have been very summer-like, bringing an illusion of summer returning. However, all the signs indicate the coming of a new season: nights are longer than days; the leaves are turning in their greens, changing into a rich palette of colours, from dull browns to golden yellows to burgundies to scarlet red; and, of course, the palette of birds is also very different than the late-summer one.

As if to celebrate the fall equinox, the first White-crowned Sparrow of the season was observed on September 21. This species breeds further north than its cousin, the White-throated Sparrow, and as thus, arrives later in fall at Cabot Head. Its breeding range in Ontario is a wide band along the James and Hudson Bays. It is the easiest sparrow to age in the fall season, adults sporting the namesake white (and black!) crown, whereas young birds have a somewhat more subdued crown of different shades of brown.

On that time of equal length of night and day, we also observed two Rusty Blackbirds exploring the rusty hull of the shipwreck, seemingly finding good morsels of food on it. There was still a hint of summer on September 21 with 10 species of warblers observed, including two American Redstarts. The redstart of September 16 was not the last one after all (I realize that I forgot to give the exact date in the previous post).

We got a few treats on the morning of September 23, starting with a fantastic, albeit short, observation of an adult Peregrine Falcon flying low, but naturally fast, over Wingfield Basin. Shortly afterward, we captured and banded an adult Yellow-billed Cuckoo. This species has been banded in nine of the previous 18 fall seasons, with only one or two birds captured, but it is the first one since 2015. We’ve had quite a few sightings and captures of Black-billed Cuckoos this year, alongside an infestation of gypsy moths: the bane of trees is also the boom of cuckoos.

It really felt like autumn on September 24 when a diverse assortment of sparrows graced the woods, with a good number flying into our nets. We banded 14 White-throated Sparrows that day, certainly the most abundant species, followed by Dark-eyed Juncos (a far second with 6 birds banded). The first White-crowned Sparrow of the season was banded. Swamp and Lincoln’s Sparrows were also present, sadly dismissed, like other sparrows, by many as LBJs (Little Brown Jobs). Yes, sparrows are not always easy to identify and their habits of skulking in dense vegetation doesn’t help. But the nuances in shades of browns and greys, in spotting and streaking, in bill shape and size, make for a wonderful challenge for whoever wants to devote some time and patience to them. Flashy spring male warblers they are not! But beauty is not just feather deep.

And now for a textbook example of migration ecology! We banded a young Mourning Warbler of undefined sex (too young to tell) on September 15, a species of thick undergrowth in disturbed and regenerating forests. After the initial banding, we recaptured the Mourning Warbler every second day up to September 23, giving us five data points for its fat and weight. So, its weight was 10.3g on September 15 and steadily climbed with time: 11.0g on the 17th, 11.7g on the 19th, 12.1g on the 21st, and finally 12.9g on the 23rd. In eight days, the Mourning Warbler increased its weight by 25%, by feeding constantly to put on fat, the necessary fuel for the long non-stop night flights of its migration. Birds do need to replenish their reserves from time to time after the demanding migratory flights: they stop in various places for sometimes extended stays, depending on their needs and the richness in food. This small example of one Mourning Warbler highlights the critical importance of “stopover” habitats throughout the length of the migratory path: without places to stop and refuel, even if their breeding and wintering habitats were safeguarded, the miracle of migration would stumble and crumble, one paved paradise at a time, one more roadside mowed instead of “messy” shrubs and weeds.

Our textbook Mourning Warbler also tied with another one, in 2017, for the latest date on record at Cabot Head. The 2017 bird was also having a stopover, banded on September 15, and recaptured five times between September 18 and 23. Unlike its 2020 counterpart, it barely managed to put on weight, another textbook example of variability in either individuals or resource availability between years. Only long-term monitoring, like the one done here at Cabot Head research Station, can provide data of this kind, allowing comparisons across years and multiple species. So, let’s keep it up!

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