The colonial nesting behavior of Purple Martins that endears them to their human hosts also makes them highly noticeable to certain predators. Any bird species that breeds in large groups tends to attract predators and a martin house full of martins and their babies is a tempting target to both land and aerial hunters. Predation is probably the biggest reason for martin colony decline and eventual abandonment. This is particularly true when an active, thriving Purple Martin colony suddenly disappears literally over night or over a few days.

It is important for a martin landlord to become knowledgeable of the characteristics and behavior of the main martin predators. Knowledge of martin predators is a valuable tool in assisting martin landlords in predator-proofing their colonies. Nothing is more heart-breaking than to have your entire martin colony wiped-out over night by a rat snake, an owl, or a raccoon, or have hawks and crows raid the martins’ nest during the day. And it can happen unless you take certain precautions to protect your martins.

The main predators of Purple Martins at their colony site can be divided into two categories: land and aerial predators. The land predators are primarily rat snakes, raccoons, and opossums. The aerial predators are mainly Great-horned, Barred, and Screech owls; Cooper’s and Sharp-shinned hawks; American Kestrels (sparrow hawks) and Merlins; kites; and crows.

The main land predators of martins are rat snakes, raccoons, and opossums. Martin landlords can easily prevent or greatly reduce the chances of this kind of predation by installing guards/baffles on the martin house poles. You must prevent the predator from climbing up the pole to raid the martins’ nests. Yet the vast majority of martin houses erected offer NO protection from land predators. Most martin landlords do not realize that these land predators can easily climb unprotected martin house poles, both wooden and metal.

Rat Snakes
Rat snakes are the primary "crawling" predators of Purple Martins and their young. These snakes are constrictors and suffocate their prey by tightly coiling around the victim. This family of snakes includes gray (often called "white oak snake" in the South), black, yellow, and red (corn) rat snakes, with the gray and black being the most common martin predators. Rat snakes can be found in nearly every area where martins nest, from the deep South to the far North, with the densest populations in the South. These snakes often hunt at night and many martin landlords never see them--but they are there, "sniffing" the air for molecules of warm blooded prey that just might be your martin colony. These snakes are the "blood hounds" of the snake family and can "smell" martins, even if the martins are "safely" 20 feet in the air in their house. I’ve seen these snakes climb 50 feet in trees to raid bird nests.

Rat snakes can climb any rustic surface, including trees, wood and brick siding. They can coil around small diameter metal martin house poles and "constrict" upward. I have seen them climb straight up cedar house siding, small and large diameter trees, one to three inch diameter metal poles, and all size diameter wooden poles, including utility poles. Many martin landlords mistakenly believe that metal poles will stop snakes; they will NOT.  When a rat snake raids a martin house, the snake will devour the martins in one nest and often coil up in that nest to digest the meal. If it is a large snake, then it may continue to raid other nests, until the snake can eat no more. If the house has young, martins in other nests will continue to feed their young as long as the adults do not see the snake. However, martins will "let you know" when they see a snake in the house by fluttering erratically around the house and not landing on it or landing on the roof. Before I predator-proofed my martin house poles, I witnessed this behavior on a number of occasions. It was not a pleasant sight to lower the house and find a huge gray rat snake coiled up in a nest with the snake’s body bulging with eaten martins.

After a rat snake has successfully raided a martin house and consume either all or a large number of the martins, then there is a strong possibility that the surviving martins will abandon the site forever. This is particularly true of small colonies with only one house. If your colony contains multiple houses, then the martins in the houses that were NOT raided will still return to nest the following year.

Raccoons and Opossums
The major four-legged martins predators are raccoons and opossums, with raccoons being the most common and dangerous. Raccoons are smart, persistent, and have some of the most "versatile" paws in the animal kingdom. Their paws can "get into almost anything", including a martin house full of martins and their babies. While opossums are more common in the South, raccoons are widespread and you can bet that they are living near your martin colony.

Raccoons and opossums are largely nocturnal and can perhaps smell the martins or hear the martins in their nests at night. These predators have no difficulty climbing non-protected metal and wooden poles to reach the martins. And once they reach the house, they will often destroy every nest in short order. Raccoons, in particular, can easily reach into the nest holes and pull the martins out. Surviving adult birds will often abandon the site after several attacks unless they have young to feed. But the young will not last long if the attacks continue. As with snake predation, surviving martins will probably not return to nest in the house(s) that was raided by raccoons or opossums.

All land predators can be easily repelled by installing pole guards.

There are two main categories of aerial predators of Purple Martins: those that hunt by night and those by day. The night hunters are the owls and the primary ones are the Great-horned owl, Barred owl, and Screech owl. The day hunters are Cooper’s and Sharp-shinned hawks, known as Accipiters; falcons, primarily Merlins and American Kestrels; kites; and crows. All the aerial hunters, except crows, will prey on both adult and young martins. Crows primarily take martin eggs and babies. Aerial hunters are much more difficult to deter than the land predators.

The key to eliminating or reducing predation by winged hunters on martins inside the houses/gourds is to install guards to the houses and gourd setups that block the predator from gaining access to the nest hole entrances. You must keep the owl, hawk or crow from landing on the house porches or hanging on the gourd holes/canopies. If the predator can gain access to the porches or gourd hole, then the martins are in grave danger.

To reduce daytime predation by aerial hunters in the immediate vicinity of the colony, insure the colony site is as open as possible so martins have a clear avenue of escape. Martins need a few seconds to build up speed to escape from Cooper’s and Sharp-shinned hawks and falcons. If martins must dodge trees and underbrush, then their forward speed is reduced, thereby maximizing the chances that a hawk or falcon may be able to overtake the martins. Also, if you can, maintain a "presence" around the martin colony site particularly early in the morning and in the evening when the martins return to roost. During these early morning or late evening hours, Cooper’s and Sharp-shinned hawks will try to ambush the martins while they are leaving or returning to their nests. Your being visible may on occasion deter these hawks from entering the immediate area of the colony.

Owls
By far, the most dangerous predators of martin colonies are owls. The three main species are the Great-horned, Barred, and Screech. Owls do their hunting at night when the martins are "safely" sleeping in their nests. Owls can successfully raid all types of unprotected martin housing, from fancy aluminum castles to swinging gourds. Owls find martin colonies as a result of the "all the noise" the martins make in their nests at night and by seeing martins moving around in houses with shallow 6"x 6" compartments. Owls have the best hearing abilities of nearly all birds and can detect the slightest sounds at night. The martins frequently hit against aluminum room dividers, scratch on gourd bottoms, move around in the nesting material, and the males even "sing" their gurgling songs. These night noises are food magnets to hunting owls and they will eventually fly to the gourd crossbars or house roof to investigate the potential prey. Once the owls determine there is food in gourds and houses, they will raid the martin colony night after night. Small colonies are wipe-out overnight. Large colonies with multiple houses/gourd poles take a long time to destroy. Many of the martins will simply abandon the site if owls are constantly tormenting the martins at night and forcing them to flee into the darkness for their lives.

Once the owl lands on the house roof top or the gourd crossbars, the owl will then listen for sounds coming from the gourds or house. If the owl is sitting on a gourd crossbar, he will often "walk like a parrot", then bend over right above the suspended gourd, "hop" off, hover for a few seconds "like a hummingbird" right in front of the gourd entrance hole, reach out with his long legs, grab the bottom portion of the hole or rain canopy, hang there, beat his wings, and then scratch with his free foot at the entrance hole. Adult male martins and non incubating/brooding females always try to escape and will often be grabbed as they try to squeeze through the hole which is partly blocked by the owl’s talons. During this struggle, thin shelled gourds maybe broken at the entrance hole when the martin is pulled out, leaving a noticeable gap at the bottom of the hole. Thicker shelled gourds may show scratch marks all over the front of the gourd. Even if the martin escapes, the martin will often abandon the colony. There is a good article with photos about how to owl-proof a gourd rack in the Article Archives section of the Purple Martin Forum at http://purplemartin.org/forumarchives/archive/owlguards.htm.

For houses, the owl simply hops off the roof and hangs onto the wide porches and guard rails. Again, adult male martins and non brooding/incubating females try to escape and they often fly right into the owl’s talons which are scratching at the entrance holes. If the owl is after young martins, he will simply insert his long legs into the shallow room and reach around into the nest until he finds a baby martin. Then the owl pulls the baby out. If you are using aluminum houses with flip up door panels, the owl will often pull them open or even off when he drags the martins out. I’ve had the door panels of the Trio houses completely dislodged and the owl carried them off with the caught martin! The wide porches with guard rails become butchering platforms for hunting owls.

It is important to understand that adult martins in early part of the season will NOT sit tight at night when a huge Barred or Great-horned owl is hanging on their gourd/house, beating his wings against the gourd/house, and scratching at the nest holes. Instinct tells the martins to get out. Even if the martins escape, martins will quickly abandon the colony if owls are constantly tormenting the martins at night and forcing them to flee for their lives into the darkness. Over a 1 week period in early March one year at my current site, a Barred owl constantly raided 3 gourds poles. All the martins abandon the site even though the owl was not successful in catching a martin every night. I would see the martins return in the evening, go into their gourds, then many would simply leave before total darkness. All the martins had abandon the site within a few days after the first week of Barred owl attacks.

However, martins will not abandon their young, though they will their eggs, because of owl attacks at night. Many of the adult martins will simply quit roosting in the houses at night if owls have been raiding the colony. Of course, the females will try to brood their small young and this places them in grave danger. Other females will no longer brood their young, and the young may die from exposure.

There are certain signs that reveal that owls are raiding your colony at night. The aluminum flip up door panels will be pulled open or even off, thin guard railings (Trio Grandpa house) may be crushed, gourd hole bottoms may be broken, the gourd fronts may show heavy scratch marks, and nesting material may be pulled out of the compartments. You also may find an occasional owl feather, which the owl lost during the raid, and plucked martin feathers under the houses/gourds or some distance away under a tree. Your martins may also show nervousness during the late afternoon. They will enter their houses/gourds, then come out and abandon the site before total darkness.

Accipiter Hawks
There are two Accipiter hawks that will prey on adult martins and their young: Cooper’s hawks and Sharp-shinned hawks. These are bird-eating raptors, with short, rounded wings and long tails. The Cooper’s hawk is larger, 15 to 21 inches in length; the Sharp-shinned, 10 to 14 inches long. The females of both species are larger than the males. They can accelerate rapidly like a feathered cheetah, twist and turn with the agility of a flycatcher, attain high speeds for short distances, and pluck their prey out of the air with their long legs. These hawks are high speed sprinters that use the element of surprise to try to capture their prey quickly.

Bold, stealthy, sleek, and fast, Cooper’s and Sharp-shinned hawks learn quickly how and when to hunt Purple Martins. They will stake out a martin colony, sit in a nearby tree, and ambush the martins, usually early in the morning or in the evening. These hawks hunt very well in dim light and try to get as close as they can to the colony without detection from either the martins or their landlord.

The Accipiter hawk’s mode of attack is surprise, accompanied by a burst of incredible speed and agility. They must get close to the martin and catch it within a few seconds, as martins can out fly any Accipiter once they are fully accelerated. They attempt to overtake martins in a short chase, following every twist and turn of their victim until the prey can be taken close to ground, from behind, or in a short climb. They also will meet martins head-on, forcing the martins to turn sharply downward with the hawk turning into the martins’ dive. They rarely chase swift birds like martins for more than a 100 feet, usually much less than this. By then, martins will have attained a greater speed than the hawk and will always escape.

Cooper’s hawks and Sharpies need cover so that they can wait and ambush adult martins at low altitudes when they are most vulnerable: socializing around their nests, on the ground collecting nesting material, flying slowly around the colony, flying to and from nests with or without young, or even flying rapidly away from the colony but near a tree where the hawk is waiting. Martin colonies located near forests or have scattered trees within 40 to 60 feet of the houses/gourds are most vulnerable. The closer the colony site is to trees and thick shrubs, the greater the danger of surprise attacks by Accipiter hawks. Martins need a clear opening to build up speed, distance the hawk, and then climb to the safety of the open skies.

Examples of Accipiter Hawk Attack
It was early March and my colony had been tormented for over a week by a female Sharpie and female Cooper’s hawk. The martin colony for all practical purposes ceased to exist and the martins no longer stayed at the houses and gourds during the day.

I was patrolling the perimeter of the colony one morning, waiting for one of the hawks to attack any martin that had not yet left the colony site. Suddenly a male martin bolted from his gourd, gained speed and quickly streaked upward. He was not more than 30 feet high when a female Sharpie exploded from a tall nearby pine tree and met the martin head on. The martin violently turned downward and the Sharpie matched the move. The martin twisted and turned from side to side while the Sharpie followed every move and was only a foot or two from the martin’s tail. The martin then pulled up abruptly in a vertical climb that took him about 40 feet up. The Sharpie also climbed and was right on the martin’s tail. But the martin was slightly faster and the Sharpie stalled out. Then the martin, emboldened by his successful escape, immediately attacked and mobbed the Sharpie as she flew into the nearby forest. But she would be back.

The male martin quickly left the area and several other martins bolted from their gourds and fled as fast as their wings would take them from the area. These martins were not attacked and quickly gained altitude and disappeared.

Not a single martin was flying overhead and no martins dared come out and sit on the gourd crossbars or house porches. But there were still some martins in the gourds and houses that peered cautiously from the entrance holes, as if waiting for some unseen signal that would tell them it was safe to leave.

I continued to walk around the colony site, as this sometimes discouraged the hawks from actually attacking martins near the houses and gourd poles. I knew the Sharpie or Cooper’s hawk was nearby.

Suddenly two female martins left one of the houses, with one martin flying very low to the ground and the other streaking almost straight up to clear the top of a pine tree that was growing near my mobile home. The high flying martin made it and quickly fled the area. The low flying martin flew into the West side of my yard that was cluttered with small pine trees and wax myrtle bushes. She made a fatal mistake, as her speed was reduced when she met the underbrush. There was a flash of wings and the Sharpie shot out from the nearby forest and was on the martin in seconds. The martin bank to the left and right, trying to dodge not only the hawk, but also trees and bushes. The Sharpie skillfully followed every move of the martin as both birds went round and round, not more than a foot or two off the ground. Within a few seconds, the Sharpie overtook the martin, caught it, and hit the ground with the screaming martin. I rushed forward, clapping my hands and screaming at the hawk. The hawk let me get within 30 feet of her before she flew off and carried the martin across the highway in front of my property where both birds disappeared in the forest.

It was a March evening and, as I always did, I was waiting for my martins to come home to roost. A Cooper’s hawk and a Sharpie had harassed my colony for nearly 3 weeks. The martins had stopped building nests and no longer stayed around the colony site at all during the day.

A huge flock of martins had assembled over the colony site and swirled through the sky in a tight mass. The martins were nervous and twisted and turned rapidly. Then they climbed higher as if trying to escape from some unseen enemy. I just knew that the Sharpie or Cooper’s hawk was either flying near the flock or was hidden in a tree waiting to attack.

It was darker now and I wondered if the martins would even come home to roost tonight. Suddenly the mass of martins came screaming down on their houses and gourds and there was total bedlam. Martins were everywhere trying to enter their nests as quickly as possible.

Suddenly a familiar, deadly shape appeared and a female Cooper’s hawk sprinted through the colony like a jet fighter, twisting and turning, trying to catch any martins within reach. The hawk climb toward my tallest gourd pole and tried to take a female martin that had missed her gourd and was turning around to try to enter again. The martin dived sharply toward the ground and the hawk tried to turn into the martin’s dive. The hawk missed and was so close to the ground that she hit a small bush. The martin escaped with a violent turn and disappeared into the fading light. I frightened the hawk away and within seconds the martin returned and entered her gourd.

It was early June and hundreds of young martins had fledged and were being fed by their parents. It seemed as though every pine tree limb in the area had family groups of martins. I watched the youngsters flutter their wings in eager anticipation as the parents brought in juicy dragonflies.

Suddenly martin alarm calls filled the air and a huge flock of adults had formed and was hovering over the top of an large oak tree. I knew it was the Cooper’s hawk. She was catching several martin youngsters a day and she was ready to eat again.

Then all the adult martins came screaming down in an incredible display of cooperative defense as the hawk flew from the oak tree and headed directly for a large family group of young martins in a pine tree. Martin after martin attacked the hawk, coming within inches of her head, back and long tail, and emitting the anti-predator mobbing call.

As the hawk approached the grouping of martin youngsters, many of the older birds immediately flew and climb into the sky. Several of the recently fledged young flew straight out into the open and the Cooper’s hawk had no difficulty overtaking one of them. The young martin screamed for a few seconds when caught and this triggered a ferocious mobbing attack by the adults. The hawk flew across an open meadow, about 200 feet from where I was standing, with a flock of angry martins on her back and then disappeared into the forest.

Falcons
The main falcons that prey on martins at their colony site are American Kestrels (sparrow hawks) and Merlins. These are both relatively small falcons, the American Kestrel being from 9 to 12 inches in length, and the Merlin from 10 to nearly 14 inches long. The American Kestrel nests throughout the range of the Purple Martin while the Merlin nests primarily in the upper northernmost range of the martin. Merlins do winter in the Southeast.

American Kestrels and Merlins have long pointed wings and long tails and are capable of high speed flight. American Kestrels largely prey on small rodents, reptiles, and insects, but will take birds on occasion. Merlins are bird-eating raptors and possess the speed to capture very fast birds, including doves, swallows, swifts, starlings, and sandpipers. Merlins and American Kestrels are swifter than Cooper’s and Sharp-shinned hawks in level flight and in a dive. However, they are not as agile as the Accipiter hawks and cannot twist and turn like a flycatcher.

Since American Kestrels nest in holes, they may on occasion attempt to raid martin nests for young and any unwary adults. American Kestrels have been known to nest in martin houses. Merlins primarily launch aerial attacks, but will also try to pull both adult and baby martins out of houses.

Though I never observed American Kestrels attacking martins, I have witnessed about a dozen attacks by Merlins on my martins and none was successful! From what I have seen, Merlins are a match for martins in level flight and are much faster in a dive. Martins can out turn and dodge a Merlin as it tries to over take them in level flight or catch them in a dive. Martins, when under attack by Merlins, try to first out maneuver the Merlins through sharp banks, dives, and quick turns. Then the martins climb at a fast rate of speed to reach the safety of high altitudes.

Merlins mode of attack on martins is somewhat similar to that of Accipiters, but with several important differences. Merlins are like "souped-up" Sharpies with a turbo-charger. They typically attack at tree top level, trying to surprise the martins. Sometimes they will even "stoop" at martins; but these dives are not comparable to that of peregrine falcons diving on prey. However, they do not have to get real close and they do not necessarily need cover like the Accipiters. When a Merlin is coming in at top speed in a slight downward direction, no martin alive can out fly this supersonic feathered bullet in level flight. But most martins, as long as they see the Merlin coming, can out maneuver and eventually out climb the Merlin. However, when a Merlin and martin are both fully accelerated and a straight level flight pursuit is ensuing (a classic tail-chasing hunt) both birds are closely matched in speed, though I still believe the Merlin is faster.

Examples of Merlin Attacks
It was late March and my martins had finally settled down to build their nests. For nearly three weeks the colony had been tormented unmercifully by migratory Cooper’s hawks and Sharpies. These hawks were gone and the colony was back to life again.

One morning the martins were busily carrying nesting materials to their nests. I had provided them with a raised platform filled with pine needles and the martins were covering it.

Suddenly martin alarm calls filled the air. Martins were flying in all directions; it looked like a beehive had been overturned. I looked up and saw a Merlin streaking through the sky above the colony site. The Merlin was over taking martins right and left, but couldn’t match the martins’ tight turns and continued speeding through the swirling mass of martins. The Merlin made one final try for a male martin that unwisely dove to escape. The martin seemed to crawl as the Merlin closed in for the kill. But the martin knew exactly what to do and banked sharply to the side and the Merlin over shot the martin by several feet. The martin then began a rapid climb to join other martins which had reached safe altitudes. The Merlin couldn’t match the martin’s climbing speed, gave up and headed North. The male martins then launched a ferocious counter attack. Martin after martin made repeated diving attacks on the Merlin. The Merlin flinched at each attack and beat a hasty retreat.

I was watching my martins one morning in early April. Nest building was still underway and more and more sub-adult martins were arriving each day.

Suddenly the predator alarm went off and the martins headed for the open sky. A small, tight flock of martins was climbing at a terrific rate of speed when suddenly the martins seemed to "explode" in different directions. A Merlin had flown directly into the flock! The Merlin was going at full speed after a female martin. Both birds were literally "on fire" as the race of life and death continued at full steam. The Merlin matched the martin’s level flight speed and closed in for the kill. The martin twisted violently to the side and the Merlin over shot, then turned around and continued the chase. The martin adeptly dodged each Merlin attack while gaining altitude at the same time. Within seconds the martin had out climbed the Merlin and joined other members of the colony which were preparing a counter attack. The Merlin dived quickly away with a flock of angry martins on its tail.

Kites
The main kite species that will prey on martins is the Mississippi kite.

Crows
The are two species of crows that will raid martin houses for eggs and babies: American crow and fish crow. The fish crow is the main culprit, particularly along coastal areas in the Southeast. Crows have no difficulty landing on martin house porches and reaching into the shallow nests with their long beaks and pulling out baby martins/eggs. Crows may not be able to hang on gourds and extract baby martins and eggs.

All martin landlords should install guards on their housing poles to deter land predators and guards to the house/gourds to prevent or reduce the chances of aerial predators from successfully raiding the colony site. Eliminating or reducing predation is one your most important responsibilities as a martin landlord. Remember: a successful predator attack on your colony will not only result in the death of your martins but may even cause total abandonment of the colony site.