Week 2: Dispersing Birds

Townsend's Warbler

Week 2 saw a drop in the number of birds banded at both stations as the period colloquially known as the “august doldrums” started. This lull in bird activity corresponds with the stage in their life history where hatch year birds are undergoing post-fledging dispersal and adults are doing their pre-basic moult. The dispersal period is interesting as it is relatively poorly understood and there are many theories as to why birds undergo it. For many species these movements seem to be fairly local as they range within a few kilometers of their natal grounds. There are several reasons/theories as to why birds might make these movements and these include:

-Prospecting:  the search for appropriate territories for the following breeding season

-Navigation:  more extensive and random movements over an area to create a “target” to aid in navigation during their return trip the following breeding season.

-Resources/survival: moving to areas with higher abundance of food and/or to avoid predators

Two Common Yellowthroats, caught together

Regardless of the birds’ intensions, what all this movement means for us banders is that we can still catch some young birds during this spell where the adults aren’t pulling their weight when it comes to hitting our nets and migration proper has yet to start. While the hatch-years are exploring, the adults take this time to moult all of the feathers on their body, including their flight feathers. As they are much less mobile and more prone to predation during this period, individual birds tend to stay within a very small area where they try to remain as unobtrusive as possible.

One of the few species we catch that is commencing migration at this point is the Pacific-slope Flycatcher. One reason for their early departure, at least of the adults, is the fact that they are one of the few species of North American long distance migrants that undergoes their pre-basic moult on their wintering grounds rather than as described above. This makes them nice and easy to age at this time of year as the hatch-years have fresh, buff-tipped wing coverts and the after-hatch-years (AHY) have worn, off white wing coverts. This week we had a spike in their numbers on Aug. 2 at Rocky Point where we caught 15 of them, almost half the 32 birds banded that day. While Pedder Bay always gets less of them we did get 10 over the course of the week. The other main catch at both stations for the week was Wilson’s Warbler with 28 at Pedder and 30 at Rocky.

Pacific-slope Flycatcher wings - age comparison

Both stations got several first of seasons this week. These included Townsend’s Warbler (each station got 1!), Hutton’s Vireo (Rocky), Red-breasted Sapsucker (Pedder) and Brown-headed Cowbird (both Rocky and Pedder). It continues to be a good year for Rufous Hummingbirds as Rocky Point banded 7 (3 on Jul. 29) and Pedder 4 bringing the season totals for the two stations to 12 and 14 respectively. At Pedder we also caught our second Anna’s Hummingbird of the season.

Outside of the nets we had some good birds as well:

-Common Nighthawk: singles heard at both stations July 28 and Rocky on the 31^st.

-Virginia Rail: one heard at Rocky a few times throughout the week.

-Semipalmated Sandpiper: 1 seen Jul. 31^st amongst 10 species of shorebirds recorded that day including our first Short-billed Dowitchers of the season.

A Young Brown-headed Cowbird

-Least Sandpiper: Pedder Bay is usually devoid of shorebirds despite some nice mudlats in the channel, but Aug. 1 did see us finally get one LESA!

-Tufted Puffin: 1 adult spotted flying west on Aug. 2^nd during moderate west winds.

-Northern Pygmy-owl: Heard first thing on the morning of Jul. 29 at Pedder.

-Bank Swallow: 1 was spotted on census flying over the back ponds at Rocky with a small flock of assorted Swallows.

-Chestnut-sided Warbler: still hanging around the banding lab, seen Aug. 2 in a large mixed chickadee/warbler flock. In very heavy moult now with all its tail feather’s dropped.

And the highlights weren’t confined to the avian variety as Serena, Sharlene and co. were fortunate enough to see a Wolf at Rocky on Aug. 1^st! The usual assortment of River Otters, Mink, Racoons and whatnot were also present throughout the week. My first  bat of the season, spotted at net opening on Aug. 2^nd seemed likely to be a Little Brown Bat based on size.

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Rocky Point	28th	29th	30th	31st	1st	2nd	3rd	Total
Banded	20	21	29	18	29	27	32	176
Species banded	13	12	14	10	11	15	11	29
Recapped	3	3	6	5	4	4	8	33
Species recapped	2	3	4	5	3	3	6	11

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Pedder Bay	28th	29th	30th	31st	1st	2nd	3rd	Total
Banded	27	20	29	22	27	12	25	162
Species banded	11	10	16	12	13	7	12	26
Recapped	9	10	2	6	11	4	2	44
Species recapped	7	6	2	4	8	3	2	13

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	Rocky Point banded	Pedder Bay banded	Total for Week 2
ANHU		1	1
RUHU	7	4	11
RBSA		1	1
WIFL	4		4
PSFL	38	10	48
HUVI	1		1
WAVI	4		4
CBCH	3	2	5
BUSH		5	5
BRCR	6		6
BEWR	3	9	12
HOWR	4	6	10
PAWR	1		1
GCKI		5	5
SWTH	5	4	9
AMRO	3	8	11
CEDW	2		2
HOFI	1	2	3
PUFI	6	5	11
PISI	5		5
AMGO	8		8
OCWA	4	1	5
MGWA	6	4	10
COYE	5	2	7
YEWA	1		1
TOWA	1	1	2
WIWA	30	28	58
SPTO	2	12	14
CHSP	4	6	10
SOSP	5	5	10
PSWS	15	25	40
ORJU	1	5	6
WETA	1	8	9
BHGR		2	2
BHCO		1	1
Total	176	162	338