Ageing and Sexing Kinglets

It was a rain-shorten day with only 10 new birds and 12 recaptures of 5 different species.  With only a 30% chance of precipitation, rain wasn't even on my radar (no pun intended) until I felt a few rain drops around 8:30am.  I checked the radar and saw the large green blob heading right to us from the ocean.  We all got pretty wet running around the banding station checking the nets for birds as we shut everything down.  

I have been waiting for about a week now to catch a female Ruby-crowned Kinglet so that I could do a post about ageing and sexing kinglets.  Finally . . .  we got three of them today!  

Male and female Ruby-crowned Kinglets look identical except for a patch of feathers on the top of their heads.  Males are adorned with a bright red feathers while the females lack the red.  Sometimes older females can have one or two red feathers in their crown.

 

In Golden-crowned Kinglets both sexes have yellow in their crowns but the male is the only one with a large patch of orange in the center.

Ageing kinglets (both Ruby-crowned and Golden-crowned) can be challenging.  Molt limits in these species are very difficult to detect.  There are couple of criteria that can be helpful when trying to age them.  The first thing we look at is the shape of the outer rectrices (tail feathers).  Like many passerines, adults will have a broader and more truncate rectrices compared to the narrower and tapered look of the juveniles.  As in the case with kinglets, the outer rectrices of adults are broader and have a club-like shape to them.  Juveniles (or hatch-years) will have more narrow and tapered looking outer rectrices.   

Another characteristic that we can look at is the primary coverts.  In adults, the primary coverts will be broader with relatively wide and distinct greenish edging.  In juveniles, the primary coverts will be more narrow with little or indistinct greenish edging,  Caution should be used when using the shape the primary coverts for ageing birds and should always be used in conjunction with other criteria.  

NEW BIRDS
3 Ruby-crowned Kinglet
1 Gray Catbird
5 Yellow-rumped Warbler (Myrtle)
1 Swamp Sparrow

RECAPTURES
7 Gray Catbird
2 Yellow-rumped Warbler (Myrtle)
1 Song Sparrow
2 Swamp Sparrow

BANDING STATS
# of Birds Banded:  10
# of Recaptures:  12
# of Species:  5
Effort:  62.1 net-hours
Capture Rate:  35.4 birds/100 net-hours
# of Nets:  23

BANDING STAFF
Aaron Given
Matt Zak
Mattie VandenBoom
Libby Natola