The last week of banding for the Spring 2021 season followed a similar pattern to the previous week. Banding was slow at the beginning of the week and picked up a little towards the end due to a brief wind shift to the west and then north. As has been the case all spring, the north and west winds didn’t last long so our biggest day was 42 birds. We had only one 100+ bird day the whole season, back on April 22. The biggest fruit crop we have seen in years from the native trees and shrubs largely fell to the ground uneaten.
Where were the migrating birds this spring? Passing by our region to the west most likely, based on overnight weather radar images. Large numbers of spring migrants generally don’t put down in our area unless the winds are out of the west or north, causing them to pause their journey. Winds were east or southerly for the majority of the spring season, providing a tailwind for the birds. The bulk of spring migration generally is over the Gulf or around the western edge through Mexico and Texas. Fall migration is shifted east enabling us to catch more birds of a greater number of species and this is the main reason we have put our effort into maintaining a continuous fall banding presence since 2002.
In spite of the lower numbers, we caught all of the species we expect to see more in spring than in fall. This last week added Bicknell’s thrush and Connecticut warbler to the roster, bringing the total to 963 birds banded of 33 species. 26 of these birds were banded in other seasons and were recaptured in 2021 either because they are residents (Northern cardinals) or wintering individuals that are using the restored habitat at Bill Baggs Cape Florida State Park year after year. The oldest of these was an Ovenbird that has been returning to spend the winter since 2012.
Thanks to all of our fantastic volunteers new and returning! This project would not be possible without you.
One of the most important food trees for migrating songbirds is the Florida Strangler fig (Ficus aurea) and they are heavily in fruit right now on our site, although there aren’t too many birds around to take advantage of it and fruit is falling uneaten to the ground. These distinctive trees are known for sending tendrils around other trees that become roots in ornate patterns. They fruit year-round but seem to be especially prolific this spring. Watch for Black-throated blue warblers with the large fruit impaled on their bills while they eat it from the inside out, eventually dropping the husk on your head as you look up at them.
We had a burst of activity on Friday May 7 and Saturday May 8 associated with another brief westerly wind shift, and caught 40 then 35 birds each day. American redstarts in particular were abundant in this wave of birds, and we started to see more young males and females.
Southeasterly winds had returned by Monday and we were back down to an 8 bird day, despite passing showers overnight and during the morning. One was this beautiful female Blackpoll with an intricate black, yellow and white plumage.
The total number of migrants captured during the last week went back down but we had some highlights that added some interesting diversity. The most notable bird is this male Mourning warbler banded today; a very rare species in South Florida. We see them occasionally in the Fall but there are very few spring records. Mourning warblers almost entirely migrate around the Western Gulf up through Texas on their way to and from breeding grounds in Canada, so this guy is pretty far off course. They are somewhat similar to Common yellowthroats and also hang out in dense understory, but Mourning warblers are brighter yellow underneath and the adult male has a distinctive dark gray head with a black bib.
Here are some of the other new species to come through in recent days:
Winds are forecast to be out of the south for the rest of this week with little rain, so we don’t expect any big numbers of migrants to settle in as the tailwind will likely carry them over us each night.
This last week did prove to be much more active, and our overall total for the season jumped from 241 to 605 birds captured. We added Yellow-billed cuckoo, Gray-cheeked thrush, Blackpoll warbler and Summer tanager to the species list, and caught a lot more of species such as Black-and-white warbler, Black-throated blue warbler, American redstart and Common yellowthroat. Several fronts worked their way down Florida in the last week, causing brief windshifts to the west and bringing us birds. The overall volume of migration has been steadily increasing, with large pulses of birds coming up overnight from western Cuba or from the southeast through the Bahamas. There have been a lot of strong southerly winds this spring which have made for a quick passage through Florida; great for birds but less exciting for birders in deep South Florida. Still, we managed to have better days this last week and broke out of the 5 to 20 birds a day rut we were stuck in for the previous 5 weeks with 46 birds on the 21st, 142 on Earth Day, 60 on the 23rd and 72 birds today. All the new volunteers were finally able to practice their extraction skills and get up to speed.
Sometimes excellent migration conditions take birds away from the Cape without replacing them. This happened over the weekend with the ripping southerly wind overnight on Saturday; all the singing Gray catbirds were gone as well as the lingering birds from the big movement on the previous Thursday. We caught 2 new birds on Sunday but were back up to 72 new birds today when the wind came around to the NW then W overnight. Flocks of warblers trickled in all morning, and they had collected in a couple patches of fruiting ficus and budding trees of other species by the afternoon. Black-and-white and Black-throated blue warblers as well as American redstarts were well-represented today. A Black-whiskered vireo sang his head off all day but never stumbled into a net. Blackpoll warblers have been noticeably absent so far this spring; I was expecting some to come in later today but nope! Usually they are moving through in good numbers by late April.
We still are waiting for a big day of banding, but the weather remains mild. The winds have been mostly southerly all week and there has been little rain, so the conditions for migrating are excellent and birds are making as much distance as possible each night. Still, more are landing at Cape Florida and our daily captures are ranging from 10 to 24 birds instead of 2 to 7. Some new species are starting to show up:
The Black-whiskered vireo is the tropical counterpart to the widespread Red-eyed vireo, and South Florida is close to the northernmost extent of its breeding range. This guy, unlike the other three warblers pictured, is probably going to stop in the area and set up a territory somewhere. They do breed on Cape Florida, but are mostly gone when we come back to band in the fall. One year we did have a male still singing on his territory around the banding station in August, so eventually we caught and banded him!
The forecast for next week calls for continued south to southwest winds and chances of rain most days. We will see if this weather interacts with the migrants to make more of them land at the Cape. The volume of birds passing over is increasing every night. Many of the ficus trees (strangler figs) have ripe fruit right now, so the buffet is set!
New species rode the E and SE winds into the area, and we captured 18 birds of 8 species on Friday April 9. Common nighthawks arrived this week, and we have heard their ‘beent’ calls every night since. The Gray catbirds have not left yet while the local Northern cardinals are getting worked up for spring.
One of the new species was this gorgeous second-year male Indigo bunting. We can tell the age of many birds by looking for molt limits; basically the difference between their original suit of feathers that grew in when they fledged and the adult feathers coming in. Many songbirds molt their body feathers in spring, giving them their colorful breeding plumage. In the case of this Indigo bunting, the juvenile feathers are brown and the new incoming feathers are turquoise.
Northern and Louisiana waterthrush are two very similar species that overlap a little in migration and on the wintering grounds, with the Louisiana waterthrush migrating earlier in spring and fall. We had both species in the hand on Friday and were able to compare them. The Louisiana waterthrush is slightly larger with a longer bill, white throat, wider supercilliary stripe and more of a ‘milk chocolate’ color to the back. Northern waterthrush have a spotted throat, darker more well-defined spots on the breast and their underparts can be yellowish. They also have a ‘dark chocolate’ color to their upperparts and their call is more metallic than the Louisiana waterthrush.
The quick rain line Friday evening disappointed us over the weekend, with fewer birds banded Saturday and Sunday than on Friday. Severe storms moved down the peninsula late on Sunday with 50 MPH gusts, and another round of storms came through overnight around 2AM or so. In spite of this rough weather we only banded 10 new birds today and recaptured an overwintering Gray catbird. Migrants were in the air according to radar, but they may have used the tailwind to get past extreme southern Florida before encountering the squall lines. This is great for the birds; weather like that would be very dangerous for birds still flying offshore.
Migrants are finally starting to trickle through the area! We had a front pass last Friday; a squall line passed late in the day and the winds shifted hard to the NW and N immediately afterwards. The timing wasn’t the greatest for getting lots of birds to fall out at Cape Florida, but there was a noticeable influx of Prairie warblers on Friday and Saturday and we banded nearly 20 of them.
The wind then continued around to the NE and is now out of the E for the rest of this week, with a new front possibly coming this Sunday or Monday. As a consequence of the wind shift the bird activity dropped again to mostly the wintering species. Gray catbirds seem to be in no hurry to leave, and they are serenading us at sunrise with their beautiful songs. A few Swainson’s warblers and Worm-eating warblers are also on the move right now, coming up from points south. We also recaptured two Northern cardinals originally banded in Fall 2019 and Fall 2020. These are one of the few species that stay year-round at Cape Florida and breed here.
We continue to catch mostly birds that have spent the winter at Cape Florida, including this Ovenbird which has come back for 9 years at least; he was banded as an adult in 2012!
Male Chuck-will’s widows are on the move, and we have banded 3 so far. We hear them singing every morning in the dark while we open the nets. This is truly a bizarre bird, and don’t let the tiny beak fool you. Their mouth opens up to be half the size of their head like a feathery Pacman.
Among the species getting ready to leave for the summer is this handsome Blue-headed vireo. They will head to forests across the Northeast US and Canada to breed. Some are singing already before they go.
We finally caught a migrating individual! This Worm-eating warbler was extremely fat, compared to the lean birds we had otherwise been catching. Fat is the fuel for migration, and the physiology of migrating birds changes to accommodate the extreme demands of the trip. The most important are the metabolic changes that make birds hungrier and cause their bodies to deposit these fat loads. Non-migratory birds usually do not carry large fat loads, so this is one way we can tell wintering individuals from those in-transit among species that winter here. The Ovenbird from 2012 was also fat, so he is getting ready to begin his migration. He is probably gone by now with all the southerly winds we have had over the last week.
The partnership between Tropical Audubon Society and the Cape Florida Banding Station is allowing us to begin regular spring migration banding for the first time in our 20-year history. We have had spring banding sessions previously in 2007, 2009-2011 and 2014 in cooperation with researchers that were using our site to collect data. Our very first bird banded this year was this Hermit thrush, an uncommon wintering species in the Miami area.
We technically have not banded an active migrant yet as it seems to be a little early. Instead we are getting an interesting sample of who has been spending the winter in the restored hardwood hammock habitat at Bill Baggs Cape Florida State Park. This is important data, even though right now we only catch a couple of birds a day. Several of these birds were banded during previous seasons, including an Ovenbird which has been returning to spend the winter here since 2014. The waves of northbound migrants will increase all through April and peak in late April or early May. In the meantime our new volunteers have time to learn where the nets are, and we are all enjoying the beautiful spring temperatures!
(Nov 7) Since 2020 insists on continuing to be weird we are ending the season under a tropical storm warning. We were expecting to be taking the nets down in the pouring rain but it held off all morning, allowing us to band until we were ready to stop. The wind was up and the skies were overcast, layered and complex like they get when something tropical is coming. I heard a thrush call while I opened nets in the dark, and when I came back by the first net I had opened, she was captured already. A very small Catharus; she measured out as a pure Bicknell’s and was our second of the season, breaking records for yet another species that is usually migrating out over the open Atlantic.