Crested Caracaras and Prescribed Burns

Back in February, while I was working on the Crested Caracara project, a prescribed burn on Buck Island Ranch (of the MacArthur Agro-ecology Research Center) left the charred remains of a few armadillos, attracting at least 50 Turkey Vultures, 20 Black Vultures, 16 Crested Caracara of varying ages, and an adult Bald Eagle.  The flames were barely out when this group of opportunistic scavengers took advantage of the situation. Historically, natural fires caused by lightning were a frequent event from every 1 to 4 years in south-central Florida, maintaining the saw palmetto and wiregrass habitat structure that is important to a number of Florida species, like the Florida Grasshopper and Bachman's Sparrow.  However, because of fire supression and poor land management practices, many areas of Florida are overgrown, and the dry prairie is a thing of the past (except at Kissimmee Prairie Preserve State Park, the biggest protected area of dry prairie left in the world).  Prescribed burns are an essential part of smart land management, especially in landscapes that have been fragmented and negatively altered by humans.  Luckily for Crested Caracaras, most of the burns on the ranch (and on other surrounding ranches) were in February during their peak nesting season.

In this photo, there are two juvenile caracaras on the edge, 2 adults in the middle,

4 Black Vultures, and 7 Turkey Vultures.

This adult pair of Crested Caracara dominated the main kill site of an armdillo.  While this looks painful for the Turkey Vulture, I am sure this isn't the first time it has been bit in the face by a Crested Caracara. From what I observed in Florida, it was harder for single adults or single immature caracaras to dominate kill sites alone (although it sometimes happened).  Pairs were understandably much more successful at it. 
 

This adult Crested Caracara is in the process of kicking and holding down a Black Vulture that wasn't getting the picture.  Pretty harsh treatment, but all of these species are very social and have a well-established pecking order (all three species roost together) which is obvious at kill sites. The Black Vulture lost and joined the Turkey Vultures at the sidelines.

Eventually, an adult Bald Eagle flew in, and cleared the carrion site. Turkey Vultures scattered and the Crested Caracara pair backed off as well. 

The adult pair of Crested Caracaras were the only birds brave enough to return to the kill site after the Bald Eagle landed.  Trust me...they are adults, but their bright yellow legs and white necks are covered in soot and ash from scavenging through the burned wetland.

 There wasn't much left by the time it got there, so the Bald Eagle didn't stay long.  Afterwards, the pair had their fill and a sub-adult Crested Caracara dominated the kill site (probably because most of it was gone, and there wasn't much to defend) But he did have his moments of glory, rattle-calling to the few remaining Turkey Vultures who weren't succesful with the adult pair around.

Most of the other Crested Caracaras (mainly juveniles, sub-adults, and single adults) on site weren't up for challenging the adult pair, and roamed the edges of this wetland that was filled with the charred remains of snakes and frogs.

Crested Caracara - juvenile (note streaking on breast, brown plumage,

buffy colored neck, pale legs and face)

Crested Caracara -juveniles foraging through recent burn

Crested Caracara - sub-adults (note overall brown plumage, horizontal dark barring on neck)

3 Crested Caracaras fighting over a snake (2 subadults in background, adult in foreground)

Crested Caracara Nest Defense, South-central Florida

While working in Florida over the winter, I spent a lot of time doing behavioral observations on adult breeding pairs of Crested Caracara.  Like most raptors, these birds are pretty territorial, and go out of their way to keep their core nest areas free of intruders.  Most often, the enemy was a passing Bald Eagle. Usually, the caracara spotted the large intruder before I did, and flew off in a fast bee-line at the  curious eagle.  Other times, the intruder was an Osprey or a Red-shouldered Hawk on a favorite perch of the adults, or a Turkey Vulture innocently passing too close. 

While watching this pair of Crested Caracara at a nest on a cattle ranch, this sub adult Bald Eagle flew in on a kettle of Turkey Vultures.  It was quickly singled out by the caracara pair and attacked, then escorted away from the nest tree.  Bald Eagles are a frequent sight in Florida, and I often saw them on carrion with vultures and Crested Caracara.  Usually, the presence of a Bald Eagle put everyone on edge, as the eagle dominated the kill site and got its choice of food.  On other occasions, Bald Eagles stayed back in the distance, and waited for the opportune moment to steal a morsel of food that caracaras were taking off to a nearby nest.  The discovery of at least one of our nests was delayed because of an adult Bald Eagle harassing an adult Caracara that was trying to take food to its mate that had been on an unseen nest.

adult Crested Caracara catching up with Bald Eagle

Pair of adult Crested Caracara tag-teaming sub-adult Bald Eagle

sub-adult I Bald Eagle

Crested Caracara - adult (notice wing molt, 5 versus 6 white primaries visible)

Crested Caracaras in Florida

adult Crested Caracara (note black plumage and bright white head feathers, in addition to bright yellow legs)

Crested Caracaras are members of the family Falconidae (which includes other species like Kestrels, Merlins and Hobbies, and the Peregrine Falcon). Recently, through genetic work, it was discovered that Falconidae is more closely related to parrots than other raptors. There are 11 known species of caracara, one of which is extinct. Crested Caracara is the only one found in the United States.

Caracara’s are named for the sound they make when they throw their head back in a “rattle” call. They are well known as Mexican Vultures or Mexican Eagles, and are found on the official seal of Mexico (with a snake in their talons). Caracaras eat carrion and also live prey, and aren’t above snatching prey from other species. I’ve seen them snatch prey from Cattle Egrets and Wood Storks, and have also seen disputes (likely territorial) between caracaras and Great Blue Herons, Osprey, Peregrine Falcons, Red-tailed Hawks, Red-shouldered Hawks, and Bald Eagles.

Caracaras have very large territories. In Florida, this territory is usually centered around clumps of cabbage palm on cattle ranches. Crested Caracaras nest mostly in Cabbage Palm, but have been known to nest in other tree species.

Population numbers of Crested Caracaras in Florida have been dropping in the last hundred years, mainly as a result of habitat destruction (combined with development pressure and road-kills). When ranch lands are converted to housing developments, factory sites, or large-scale agriculture, the Cabbage Palms that Caracaras depend on are cut, and pairs are displaced off their breeding territories. Pairs do seem to mate for life, and once a territory is established, the pair will likely remain on it for the rest of their lives. A 16 year old caracara was recently recovered as a road kill, and it had moved only 9 km from where it was banded as a sub adult.

You may see caracaras on the edge of cities or developments. My guess is that these are birds that have been displaced by development elsewhere, or they are birds that are attempting to hold out on their historic territories until the habitat can no longer meet their needs. Caracaras may actually appear to benefit initially from construction; they are attracted to recently burned areas, recently cleared ditches, and recently cleared brush piles, where they are likely to find a large concentration of lizards, frogs and bugs to eat. But these benefits are only temporary; if the Cabbage Palms that they depend on are taken out, the birds will likely abandon their territories in search of more suitable habitat.

The project I am working on seeks to find out specifically how breeding pairs of Crested Caracara react to large-scale development on and near their territories. Many of our focal pairs nesting areas are not directly on proposed project sites, but are on the edge of these lands. Because caracaras have such large territories, which do overlap on these project sites, one can hypothesize that home range will either shift or shrink, depending on suitability of surrounding lands. If caracaras are particularly sensitive to a certain type of development (that is, if their Cabbage Palms/nesting trees are cut and/or their foraging/roosting areas are destroyed or decreased to some level), it is likely they will move on, to “greener pastures.” Unfortunately for a caracara, greener pastures are few and far between in Florida. And, if they do find such an ideal land (cattle ranch), they most likely won’t be welcomed with the label of an endangered species.

While there are laws and regulations that govern the extent of development allowed, I can only hope that private landowners can continually recognize the importance of this species, and work towards common goals of land preservation and stewardship. For a species with such a small range in Florida, a displaced caracara has only so many places it can retreat to.

The following is a collection of photos of Crested Caracaras in juvenile plumage, and one in sub adult plumage.  Notice the streaked pattern on the neck and breast of juveniles, as opposed to the barred pattern on sub adults and adults.  Also note the overall brown plumage, "bulging" eyes, and pale grey legs. Alex wrote a good summary post on how to age Caracaras while he was visiting, which you can find at this link Nemesis Bird

Crested Caracara - juvenile

Crested Caracara - subadult

 

Crested Caracara - juvenile

Crested Caracara - juvenile

 

Crested Caracara - juvenile