Basics of the Prebasic

CAPTAIN SAMS

We are in a bit of a lull after the first migrant push. 1 bird newly banded and 2 recaptured today at Captain Sam's. We recaptured a Brown Thrasher that was banded in 2024 as a hatch year, which means that this bird is approximately 2 years old.

The thrasher was currently doing a prebasic molt: an annual process that songbirds undergo after each breeding season to replace body and flight feathers.

For most songbirds, prebasic molts are complete (they replace everything), and occur in a similar and predictable manner. The flight feathers get molted in a specific sequence. Below I include a few photos from the previous banding sessions to illustrate this sequence.

Flight feather molt starts with p1 and continues outward. The corresponding primary covert gets molted with the primaries. In the picture below, the bird is molting the first few primaries, and you can see the outward progression based on the feather length.

Northern Cardinal (after hatch year, female) molting first few flight feathers

When the first few primaries are molting, the bird may also be molting its tertials. When the bird gets to molting p5 (or approximately that position), s1 starts molting.

House Finch (after hatch year, sex unknown) beginning secondary feather replacement

The secondaries molt inwards (towards the body).

Painted Bunting (after hatch year, female)

Below is the thrasher we banded today. The bird is just completing its prebasic molt. The outer primaries (p8, p9 and p10), and the inner secondaries (s5 and s6) are just coming in. The bird was also actively growing its tail feathers (not pictured). No flight feathers remain from the previous year.

Brown Thrasher (after hatch year, sex unknown) finishing up the prebasic molt

Jasmine

LITTLE BEAR

It was also another slower day at Little Bear. The temperature rose very quickly and it hit 90 degrees right around 9AM so we closed up early today. We ended up with 13 birds of 7 species with 9 newly banded birds and 4 recaptures. Painted Buntings accounted for most of our new birds today, with 5 banded. Our recaptured Prairie Warbler was very fat, so at least the birds that have stopped at Little Bear are finding plenty of food to fuel the journey south. 

The slower days have given us time to explore the area with ponds just past one of our nets and put up a net across the sand flats. We were rewarded today with the capture of a Least Sandpiper! There are a few small shorebirds moving through the region right now and they are known for being difficult to ID while birdwatching. A few things that set Least Sandpipers apart are their very small size, dark brown back and breast, slightly downcurved bill, and green legs. 

Least Sandpiper, hatch year unknown sex

We determined this to be a hatch year based on the uniformly fresh feathers with extensive buffy edging on the upper wing coverts and back feathers. This species molts on the wintering grounds, so adults would be starting their prebasic molt and have a mix of worn feathers that contrasts with the fresh, new feathers.  Maybe we will be able to capture a few more throughout the season and see a few examples of different ages!

-Liz

Species	Captain Sam's		Little Bear
	New	Recaps	New	Recaps
Least Sandpiper	-	-	1	-
White-eyed Vireo	-	-	1	-
Carolina Chickadee	-	1	-	-
Tufted Titmouse	-	-	-	1
Brown Thrasher	-	1	-	-
Ovenbird	1	-	-	-
Northern Waterthrush	-	-	1	-
Prairie Warbler	-	-	-	1
Northern Cardinal	-	-	1	1
Painted Bunting	-	-	5	1
	-	-	-	-

Today's Banding Stats	Captain Sams	Little Bear	TOTAL
# Birds Banded	1	9	10
# of Recaptures	2	4	6
# of Species	3	7	10
Effort (net-hours)	105.6	84	189.6
Capture Rate (birds/100 net-hours)	2.8	15.5	8.4
# of Nets	33	28	61

2026 Fall Cumulative Banding Stats	Captain Sams	Little Bear	TOTAL
# Birds Banded	536	289	825
# of Recaptures	151	74	225
# of Species	32	29	40
Effort (net-hours)	3459.4	1,939.1	5,398.5
Capture Rate (birds/100 net-hours)	19.9	18.7	19.4
# of Days	26	19

Banding Staff

Aaron Given (CS)

Michael Gamble (CS)

Liz Held (LB)

Olivia DeMarchi (LB)

Jasmine Fu (CS)

Aiden Gifford (LB)

Note:  All banding, marking, and sampling is being conducted under a federally authorized Bird Banding Permit issued by the U.S. Geological Survey’s Bird Banding Lab.