Razorbills Invade Florida

Source: eBird : December 20

Razorbills are alcids of the cold North Atlantic waters and rarely strays south of Cape Hatteras, NC, in the United States. The state of Florida previously had 14 records of this species, so last week when multiple Razorbills started appearing in Florida—including flocks of more than 20 birds—it was clear that something very odd was going on.

This invasion has continued to strengthen, with some Razorbills turning up as far south as Miami and the Florida Keys, and some remarkable birds apparently rounding the tip of the peninsula and appearing along the Gulf coast!

Some other species more typical of the Northeast and mid-Atlantic are also turning up, including Black Scoters, Dovekie, and even the Thick-billed Murre.

This invasion of the Southeast is helping to lend perspective to odd patterns in coastal southern New England. Although alcids are sometimes driven by storms to unusual places, large-scale invasions like this are more typically driven by food shortages in their normal range.

Here are just a few of the more notable counts from eBird so far:

• 50 at South Inlet Park, Ft. Lauderdale, 14 Dec 2012
• 200 at Boynton Beach Inlet Park, Palm Beach Co., 14 Dec 2012
• 450 off Miami, 14 Dec 2012
• 500 off Palm Beach County, 14 Dec 2012
• 32 at Government Cut, Miami, 15 Dec 2012

This invasion would be noteworthy enough if these were all single birds, but some huge flocks of Razorbills are occurring, with the highest counts so far being up to 450 seen off the coast of Miami!

Just to remind you- the entire state of Florida has had just 14 prior records and Miami-Dade County had just one prior record! This year is amazing!

One additional thing to pay attention to is the age of Razorbills that are seen well. Immature Razorbills, lack any vertical white stripes on the bill. Winter adults, on the other hand, have obvious vertical white lines in the middle of the bill—it seems that the majority of birds in this invasion are first-winter birds.

Are records of Razorbills, Thick-billed Murres, Dovekies, Red-throated Loon, and Black-legged Kittiwakes close to shore in the Northeast connected to this movement? Can records from the Carolinas and Georgia be connected to the movement into Florida? Are Razorbill counts off the Northeast coast depressed this year or are numbers high here as well suggesting even larger scale movements?

The core range of Razorbill in winter is offshore and nearshore waters, mostly over the Continental Shelf, from the Atlantic Provinces in Canada south to the Mid-Atlantic states and Cape Hatteras, NC. In exceptional years, large numbers invade south to Cape Hatteras and a few straggle further south, although the causes for these invasions are rarely clear.

Changes in the distribution of wintering alcids are often food-driven, and if waters in their core range are unusually unproductive, many birds may wander (south, in this case) in search of suitable conditions and richer food sources. Razorbills eat mostly capelin (a small fish in the smelt family) in the northern breeding range and herring and sandlance in southern breeding range) in summer (fide Tony Diamond). The diet is probably similar in winter, with capelin and krill (small crustaceans) especially important during the winter (see e.g., Gaston and Woo 2008, Lilliendahl 2009). Availability of these food sources probably is driving the current invasion, so information on the abundance of these species relative to past years would be an important piece of the puzzle.

In many ways the alcid invasion probably parallels the finch invasion underway across the northern reaches of the United States now, with both species of crossbills, redpolls, and Pine Grobeaks dispersing farther and farther south in search of suitable food. To support our theory that the southward alcid invasion is food driven, we looked at ocean temperatures in the western North Atlantic, including temperatures at or near the Continental Shelf where Razorbills and many other species winter.

This fall, particularly in November, has seen an unusually large Sea Surface Temperature (SSTs) anomaly off the Northeast Coast. Along the Continental Shelf from Long Island to George’s Bank (east of Massachusetts), SSTs are approaching 4 C above normal (they are presently or have been approximately 10-15 C rather than 6-11 C). This anomalous event presumably results in significant changes in the distribution and types of fish and other food available for foraging; this is exactly the type of environmental change that would fuel long-range dispersal such as that being seen in Florida right now.

Although this is certainly exciting for Florida and Gulf coast birders, it is difficult to view this as good news for the birds. Razorbills and the other species invading Florida have adapted over millions of years to feed on a certain assemblage of sea life in a range of sea surface temperatures. If the marine system starts changing rapidly and quickly becomes something unfamiliar to Razorbills and other species, it may have profound impacts on their populations.

Perhaps the recent Razorbill invasion should be viewed simultaneously as an exciting chance to see these remarkable birds in Florida and document an unprecedented invasion, while at the same time recognizing that it probably signals birds making desperate attempts to flee a home that suddenly became unfamiliar and inhospitable. Moreover, there is the question of whether the 2012 invasion is an anomaly or marks the beginning of a frightening trend.

Posted by Marshall Iliff (Team eBird), Andy Farnsworth (Team BirdCast), and Tom Johnson, with editorial comments by Brian Sullivan (Team eBird), Matt Hafner, Tom Reed, Tony Diamond, and several others.

Photos Courtesy of Trey Mitchell