Monday, December 7, 2020

2020 Fall Migration Summary

The 2020 fall migration banding season at the Kiawah Island Banding Station (KIBS) concluded on Monday, 30 November. We banded at two sites on Kiawah Island again this fall:  Captain Sam's and Little Bear.  This was the 12th consecutive year of fall migration banding at the Captain Sam's site with banding occurring daily during the last 9 years.  It was the 6th season for the Little Bear site which we initiated during the fall of 2015.  The two sites are located at each end of island about 8 miles apart (Captain Sam's on the west end, Little Bear on the east end).  Both sites are situated in coastal scrub/shrub and high marsh habitats, however, the Little Bear site is in an earlier stage of succession. Collectively, we banded 7,199 birds and had 1,674 recaptures of 92 different species.  Captain Sam's had a small decrease in the number of birds banded compared to last year, while Little Bear showed a moderate increase.  Captain Sam’s and Little Bear combined, experienced a less than 1% increase in the number of birds banded from last year.  We had 12 fewer species than our record-breaking year last year but species diversity was still around the average over the last 9 years.   

It was a hot and humid August and September but that didn’t seem to stop the birds from moving south as we had an above average start to the season.  The first half of October was very busy, but migration slowed down substantially after mid-October and through the end of November.  November experienced above average temperatures which probably contributed to the relative paucity of later migrants like sparrows, kinglets, and Yellow-rumped Warblers.  Despite the 2020 Atlantic hurricane season breaking records with 30 named storms, this is the first year since 2014 when we didn't have to shut down the station for an extended period due to a tropical storm, hurricane, or 1000-year flood.    

CAPTAIN SAM'S

Nets were opened for a total of 104 days from 15 August - 30 November.  There were only 4 days when banding did not occur because of inclement weather (8/23, 9/9, 11/12, 11/30).  We banded 4,566 new birds of 80 different species.  The most commonly banded species were Gray Catbirds (897), Common Yellowthroats (880) and Yellow-rumped Warbler (509).  Those three species combined made up 50% of all the birds banded this season.  Gray Catbirds took over the number one spot this year after exhibiting a 27.5% increase from last year.  Catbird bird numbers were also 20% higher this year compared to the average of the last 9 years.  Alternatively, Common Yellowthroats decreased by almost 28% from last year and 22% over the average of the last 9 years.  Yellow-rumped Warbler numbers continue to decline and were down 22.4% from last year and over 32% from the average of the last 9 years.  This trend is alarming because KIBS isn’t the only banding station in the east that is seeing this trend. 

Several species exhibited record high numbers this season:  Swainson’s Thrush, Gray-cheeked Thrush, Ovenbird, American Redstart, and Blackpoll Warbler.  Alternatively, we had a few species that had record low numbers:  Ruby-crowned Kinglet, Song Sparrow, and White-throated Sparrow.   

The overall effort increased slightly from 13,103.7 net-hours in 2019 to 13,734.03 net-hours this year.  We banded 20 more birds this year compared to last year, and 5 birds more than the average for the previous 9 years.  The capture rate decreased slightly by 3.3 birds/100 net-hours compared to last year but was 8.8 birds/100 net-hours lower than the 9-year average of 50.5 birds/100 net-hours.  Our capture rate has decreased every year starting in 2012 with exception to 2017 and 2019 when we experienced small increases from the previous year.  The capture rate of recaptures is very consistent from year to year; therefore, all decreases in the total capture rate can be attributed to new birds.

We had 1,166 recaptures which is slightly lower compared to last year.  We recaptured many individuals that were banded in previous years.  It will take a while to sort through all those records to determine how many unique returns we had as some of those were undoubtedly captured more than once during the fall.  We did not recapture any birds that were banded at a different location.

There were 9 days this fall when over 100 birds were banded compared to 12 days last fall.  The best day of the season was on 1 October when we banded 262 birds and had 9 recaptures.  The next two busiest days occurred 2 and 3 October when 256 and 240 birds were banded, respectively.  The 10-day period between 27 September and 6 October accounted for nearly a third of all the birds banded for the entire season. 

We captured one species that has never been banded at the Captain Sam's site during the fall:  Connecticut Warbler.  This was also the first time a Connecticut Warbler has been documented on Kiawah Island!  This species is one that I would have expected to have captured by now due to their east coast migration route, but they have evaded us until this year when we captured two of them (and another at Little Bear). 

Some other rare and notable species that were banded this fall include:  Common Ground Dove (1), Eastern Whip-poor-will (1; 3 previous), Red-breasted Nuthatch (3; 11 previous), Brown Creeper (2; 9 previous), Clay-colored Sparrow (2; 7 previous), Blue-winged Warbler (1; 2 previous), Mourning Warbler (1; 2 previous), Black-throated Green Warbler (1; 5 previous).      

Species notably absent this year included:  Eastern Screech-Owl, Acadian Flycatcher, Marsh Wren, Swainson’s Warbler, and Nashville Warbler.  Since 2012, Acadian Flycatchers have been an annual capture with exception to 2015 and 2020.  Nashville Warblers have only been missed in 2018 and 2020.     

Top 10 Species Banded at Captain Sam's

1.  Gray Catbird (897)
2.  Common Yellowthroat (880)
3.  Yellow-rumped Warbler (509)
4.  American Redstart (369)
5.  Red-eyed Vireo (220)
6. Northern Waterthrush (180)
7.  Painted Bunting (171)
8.  Palm Warbler (148)
9.  Black-throated Blue Warbler (111)
10.  Prairie Warbler (101)

LITTLE BEAR

Nets were opened for a total of 79 days from 24 August - 17 November.  Little Bear opened a couple days later than normal this year due to the timing of the availability of housing for the seasonal banders.  Fortunately, we were able to extend the season by a couple of days at the end.  There were 7 days cancelled due to bad weather (rain and/or wind).  Because the habitat at Little Bear is more open than at Captain Sam’s, wind has a much bigger effect on the operation of the nets there.  As a result, 4 or 5 days were cancelled due to wind alone at Little Bear this year.   

We banded 2,633 new birds of 71 different species.  The most commonly banded species were Gray Catbirds (568), Common Yellowthroat (531), and Yellow-rumped Warbler (172).    Those three species combined made up 48% of all the birds banded this season.  Like Captain Sam's, Gray Catbird numbers exhibited an increase (6%) compared to 2019 but showed a larger decrease of almost 8% over the last 6 years.  Common Yellowthroat decreased by 15% compared to last year and 14% compared to the average of the last 6 years.  Yellow-rumped Warblers made it into the top 3 this year with an increase of 64% from last year.  Unfortunately, they are still experiencing a decline of 41% over the last 6 years.  Locally, the long-term negative trend for Yellow-rumped Warblers at Little Bear can partly be attributed to saltwater intrusion that killed many of the mature wax myrtles in 2015 and 2016.  Yellow-rumped Warblers feed on the berries of wax myrtles and without that resource available a decrease was evident.  However, Yellow-rumped Warbler numbers have also been decreasing at Captain Sam’s over the same time period where the wax myrtles have not succumbed to salt water therefore there may be other factors causing this population decline.  Some of the wax myrtles at Little Bear have rebounded which might explain the increase of Yellow-rumped Warblers at Little Bear this year.

Some of the same species that exhibited record high numbers at Captain Sam’s did so at Little Bear too:  Swainson’s Thrush, American Redstart, and Blackpoll Warbler.  Species that had record low numbers include:  Song Sparrow, Yellow Warbler, and Cape May Warbler.     

We logged 7836.82 net-hours out at Little Bear this fall – a large increase from the 5,462.4 net-hours in 2019.  Three additional nets were added at Little Bear this year which accounts for only 895.0 net-hours (38%).  These nets were added in areas where the effects of wind might be reduced therefore allowing Little Bear to operate during windier conditions.  Little Bear was also open for 4 more day this year compared to last year.  In general, the nets were kept open later into the day this year than usual which helped contribute to the increased effort.  Because less birds are captured later in the morning, I believe this also contributed to the substantial decrease in the capture rate we experienced this year (see below). 

We banded 74 more birds this year compared to last year but 252 birds fewer than the 6-year average.  Little Bear’s capture rate decreased 27% from 55.3 birds/100 net-hours in 2019 to 40.1 in 2020.  Similarly, the capture rate has decreased 34% compared to the 6-year average.

After 3 years in a row where we have seen a substantial decrease in the number of recaptures, Little Bear experienced an increase in the number of recaptures this year compared to last year (460 in 2019 and 507 in 2020).  The increased effort this year most likely was the reason as the capture rate of recaptures decreased by 2.0 birds/100 net-hours from last year. 

Like in 2019, there were only 4 days when over 100 birds were banded but had 3 days in the 90’s.  The best day of the season was on 1 October when we banded 140 birds and had 4 recaptures.  The next two busiest days occurred 30 September and 2 October when 116 and 119 birds were banded, respectively. 

We captured five species never banded at Little Bear during the fall:  Ash-throated Flycatcher, Black-whiskered Vireo, Louisiana Waterthrush, Connecticut Warbler, and Golden-winged Warbler.  This is the first time a Black-whiskered Vireo has ever been recorded on Kiawah Island.  Additionally, it is only the 2nd record of this species in South Carolina.  Black-whiskered Vireos are found throughout the Caribbean and only reaches the US regularly in south Florida.     

Some other rare and notable species banded include:  Least Flycatcher (1; 4 previous), Warbling Vireo (1; 2 previous), Lincoln’s Sparrow (2; 3 previous), Blackburnian Warbler (1; 2 previous), Bay-breasted Warbler (1; 2 previous).

Species notably absent: Acadian Flycatcher, Great-crested Flycatcher, House Finch, Field Sparrow, and Nashville Warbler.

Top 10 Species Banded at Little Bear

1.  Gray Catbird (568)
2.  Common Yellowthroat (531)
3.  Yellow-rumped Warbler (172)
4.  Painted Bunting (152)
5.  Palm Warbler (146)
5.  American Redstart (146)
7.  Red-eyed Vireo (122)
8.  Northern Waterthrush (110)
9.  House Wren (61)
10. Black-throated Blue Warbler (53)

ACKNOWLEDGEMENTS

Without the cooperation of many people and entities, this work would not be possible.  The success of this project relies on their commitment, and I am in a debt of gratitude to everyone involved. 

First, I'd like to thank my awesome team of banding assistants (Kristin Attinger, Josh Lefever, Dan Errichetti, Vince Weber, Sarah Stewart, and Sarah Mueller).  Their hard work over the course of this long season was outstanding.  It was a fun season and I would like to wish them all the very best of luck in the future. 

The 2020 KIBS Banding Crew
From left to right: Sarah Stewart, Dan Errichetti, Josh Lefever, Vince Weber, Kristin Attinger, Aaron Given.  Not pictured: Sarah Mueller

Next, I'd like to acknowledge the Town of Kiawah Island for providing funding for equipment and banding assistant stipends, the Kiawah Island Conservancy for providing funding for the housing of the banding assistants, and the Kiawah Partners and the Bear Island Holding Trust for allowing access to their property for banding. 

This is usually the part where I thank our awesome volunteers but I because of restrictions due to COVID-19 we did not allow any volunteers or visitors at the banding station.  We sure did miss having their help this year and hope to have them back again next year.   

-Aaron


SPECIES

CAPTAIN SAM’S

LITTLE BEAR

New

Recapture

New

 Recapture

Common Ground Dove

1

-

-

-

Mouning Dove

4

-

-

-

Yellow-billed Cuckoo

12

-

5

-

Chuck-will's-widow

-

-

2

1

Eastern Whip-poor-will

1

 

2

 

Sharp-shinned Hawk

2

-

-

-

Eastern Screech-Owl

-

-

4

1

Yellow-bellied Sapsucker

6

1

4

1

Downy Woodpecker

5

15

4

1

Ash-throated Flycatcher

-

-

1

-

Great Crested Flycatcher

4

2

-

-

Eastern Kingbird

3

-

3

-

Eastern Wood-Pewee

7

-

5

-

"Traill's" Flycatcher

23

3

16

-

Least Flycatcher

1

-

1

-

Eastern Phoebe

29

9

29

-

White-eyed Vireo

75

37

48

16

Blue-headed vireo

4

-

3

-

Warbling Vireo

-

-

1

-

Red-eyed Vireo

220

17

122

3

Black-whiskered Vireo

-

-

1

1

Carolina Chickadee

4

23

4

8

Tree Swallow

28

-

-

-

House Wren

45

14

61

6

Marsh Wren

-

-

2

-

Carolina Wren

14

65

16

52

Brown Creeper

2

1

-

-

Red-breasted Nuthatch

3

-

-

-

Blue-gray Gnatcatcher

8

1

4

2

Golden-crowned Kinglet

8

1

-

-

Ruby-crowned Kinget

63

13

31

2

Veery

17

-

3

-

Gray-cheeked Thrush

10

-

6

-

Swainson's Thrush

95

2

30

-

Hermit Thrush

21

24

4

2

Wood Thrush

1

1

-

-

American Robin

6

-

1

-

Gray Catbird

897

374

568

185

Brown Thrasher

15

14

2

2

Northern Mockingbird

16

4

13

2

House Finch

2

-

-

-

American Goldfinch

1

-

-

-

Eastern Towhee

5

15

6

6

Clay-colored Sparrow

2

-

-

-

Field Sparrow

-

1

-

-

Savannah Sparrow

6

-

2

-

Saltmarsh Sparrow

2

-

-

-

Song Sparrow

24

9

20

4

Lincoln's Sparrow

-

-

2

-

Swamp Sparrow

47

17

39

5

White-throated Sparrow

5

3

3

2

White-crowned Sparrow

1

-

-

-

Yellow-breasted Chat

13

1

8

-

Baltimore Oriole

2

-

2

2

Ovenbird

51

13

26

2

Worm-eating Warbler

9

4

5

-

Louisiana Waterthrush

-

-

1

-

Northern Waterthrush

180

49

110

13

Golden-winged Warbler

-

-

1

-

Blue-winged Warbler

1

-

-

-

Black-and-white Warbler

43

2

17

-

Prothonotary Warbler

11

1

2

-

Swainson's Warbler

-

-

2

-

Tennessee Warbler

1

-

3

1

Orange-crowned Warbler

20

6

13

1

Connecticut Warbler

2

-

1

-

Mourning Warbler

1

-

-

-

Common Yellowthroat

880

69

531

62

Hooded Warbler

7

-

3

-

American Redstart

369

23

146

6

Cape May Warbler

13

-

14

1

Northern Parula

35

1

23

2

Magnolia Warbler

10

-

1

-

Bay-breasted Warbler

-

-

1

-

Blackburnian Warbler

-

-

1

-

Yellow Warbler

33

-

21

2

Chestnut-sided Warbler

1

-

-

-

Blackpoll Warbler

19

2

14

1

Black-throated Blue Warbler

111

3

53

2

Palm Warbler

148

3

146

3

Pine Warbler

2

1

-

-

Yellow-rumped Warbler (Myrtle)

509

82

172

7

Yellow-throated Warbler

1

-

2

-

Prairie Warbler

101

8

52

9

Black-throated Green Warbler

1

-

-

-

Summer Tanager

4

-

2

-

Scarlet Tanager

3

-

2

-

Northern Cardinal

30

111

28

36

Rose-breasted Grosbeak

2

-

-

-

Blue Grosbeak

2

-

1

-

Indigo Bunting

35

1

9

1

Painted Bunting

171

120

152

54

 

BANDING STATISTICS

CAPTAIN SAM'S

LITTLE BEAR

TOTAL

# of Birds Banded

4,566

2,633

7,199

# of Recaptures

1,166

507

1,673

# of Species

80

71

92

Effort (net-hours)

13,734.6

7,839.8

21,571.5

Capture Rate (birds/100 net-hours)

41.7

40.1

41.1

# of Nets

30

23

53

# of Days Operated

104

79

-

Dates of Operation

8/15-11/30

8/24-11/17

-


Please note that these numbers are preliminary and may change after the data has been thoroughly proofed.