Multiple Cooper's Hawk Attacks On Martin Fledglings

[Steve Kroenke]

Example Of Multiple Cooper?s Hawk Attacks On Martin Fledglings

During the 2005 purple martin season, my next door neighbor?s (Bob) colony and my new one were under siege from a pair of resident Cooper?s hawks that preyed extensively on the martin fledglings. We had over 250 pairs of martins nesting which produced around 1000 fledglings. I estimate the hawks killed about 10 % of the youngsters and most were caught at various purple martin family assembly sites located in tree canopies or on utility lines. These sites were often near our colonies and I could observe the hawks attacking the fledglings and the parent martins mobbing the raptors.

I have seen this predatory behavior many times in the past at my previous martin colonies in north Florida and I have lost hundreds of fledglings to bird eating Cooper?s hawks. These Accipiter hawks are deadly enemies of both adult and young martins and will stake out colonies and hunt the fledglings which lack the flight speed and agility to escape. Many martin colonies located throughout the United States and Canada will have resident Accipiters, both Cooper?s and sharp-shinned hawks, which prey on the fledglings. Larger colonies probably experience greater predation because of more prey for the hawks.

The hawks that attacked our colonies were apparently nesting west to northwest of our colonies in a deep forested area toward the Texas line. An open cow pasture separates this timber from our martin colonies and the hawks often flew across this area. I believe their nest was about a mile or two inside the forest and I plan to search for it this fall when there is less foliage in the trees.

The hawk predation occurred from early June through mid-July and with most during mid to late June. On some days, both male and female hawks would make repeated visits and attacks, often killing several martin fledglings that I saw. The hawks always carried their prey directly to the same location which I assumed was their nest site or perhaps where their fledglings were assembled. I would try to follow their flight direction with my binoculars and they would then drop down into a dense area of hardwoods. Cooper?s hawks laden with prey will often fly in a straight line to their nests.

The parent martins made numerous but futile mobbing attacks on the hawks which largely ignored them. I would often see a hawk approaching the area either at a high altitude or just over the treetops and a huge mob of screaming martins would be following and attacking. The hawk kept on going and continued to search the area for vulnerable martin fledglings.

Cooper?s hawks, like most raptors, have fantastic eyesight and can see a tiny martin fledgling sitting on a utility line or flying with its parents from great distances. The parent martins always screamed in terror when these hawks approached high in the sky and this warned me. I would observe these hawks dropped from the heavens like feathered rockets with their wings against their sides and grab a helpless martin fledgling which had no hope of escaping. The adult martins attacked the diving hawks but it was completely futile as the hawk quickly realized that these mobbing assaults are all bluff.

I was able to intervene and chase the hawks away from our colonies provided I knew the raptors were overhead and they could easily see me. The hawks would not attack if I confronted them in the open and clapped my hands. In fact, I prevented a number of direct attacks on martin fledglings that were sitting on utility lines adjacent to our colonies or on gourd crossbars by rushing at a diving or circling hawk. Several of these attacks were spectacular stoops with the hawk flaring up to grab a fledgling and then seeing me rushing forward and clapping my hands. I was unable to prevent attacks farther away from our colonies and the hawks had an easy time predating these helpless martin fledglings.

For a number of days I recorded the number of Cooper?s hawks visits/attacks and the outcomes. On June 9, 2005, the deadly female hawk was particularly active and inflicted considerable terror on both our martin colonies. You would have to be there to understand what a Cooper?s hawk can do to the harmony of a martin colony. The parent martins screamed and screamed and screamed as they desperately tried to protect their fledglings. I did what I could to intercept these killers before they could reach the martin fledglings, but I simply couldn?t be everywhere.

Here is what happened on June 9, 2005?

At around 7:40 am the female Cooper?s hawk came from the northeast at several hundred feet above our colonies and I greeted her between our yards. She saw me, turned and went directly north where some fledglings were sitting in a dead tree. She folded her wings against her sides and plunged downward in a twisting rapid dive while numerous screaming adult martins pursued her to almost ground level. The martins were in a frenzy as they came within inches of the hawk it seemed. I am almost certain she caught one of the fledglings.

At around 8:50 am, she returned from the west (where her nest was most likely located) and crossed a wide pasture. She was heading directly for an oak tree located several hundred yards from my colony which had some martin fledglings in the top canopy. There must have been a hundred martins attacking the hawk as she climbed above the tree and circled it, looking for the fledglings. The screams of terror coming from the parent martins were so loud that they seemed electronically amplified. Martin after martin attacked the hawk which then dropped down in a circuitous flight and appeared to grab one of the fledglings. This action caused the entire group of martins to mob the hawk which carried her victim across the pasture to another oak tree. Using my binoculars, I could see the hawk sitting in the top of the oak. A scissor-tailed flycatcher was making repeated diving attacks at the hawk. Then the hawk carried the prey deeper in the woods.

At around 10:00 am, my colony erupted into a screaming mass of martins that climbed rapidly; Bob?s martins joined in the flight upward. They were like fighter pilots climbing to meet the enemy and engage her in battle! Coming from the southwest at several hundred yards high up with her wings curved back was the deadly female Cooper?s hawk. This is a hunting profile and usually signals a spectacular stoop. But I was standing directly under my colony and clapping my hands loudly. These hawks have fantastic eye sight and she obviously saw me and kept on going with a mob of martins on her.

At around 11:15 am, she appeared high over a woodlot several hundred yards to the northeast of our colonies. She was heading directly to area where she most likely caught a martin fledgling earlier in a dead tree. It seemed as though every martin in our colonies was after her and she ignored them. She circled over and over again the area as if she was looking for a victim. The poor martins were screaming at top volume and making repeated mobbing attacks. Then she dove down in a spiraling maneuver with numerous parent martins screaming and following her. I believe she most likely got another fledgling though I am not certain.

At around 3:40 pm, the martins in Bob?s colony exploded from their nests and streaked directly north. Coming at a slow pace about 50 feet off the ground from the north and flying down a fence line that has some sweet gum trees growing along it was the female Cooper?s hawk. She ignored the martins? mobbing and continued straight for about a 25 foot tall sweet gum tree that had some fledglings in its top canopy. I ran all the way from my yard and tried to reach Bob?s colony site in time, but the hawk streaked downward, caught a fledgling, and flew briefly to the ground. His entire colony was now a boiling witches? cauldron of screaming martins! The hawk, laden with her kill, flew across another pasture about 200 feet from Bob?s colony with a pack of martins attacking her.

That was the last visit by the Cooper?s hawks on June 9, 2005 that I saw. However, both male and female hawks continued to raid the many purple martin family assembly sites located near our colonies and predated the fledglings. Nearly every day from early June through mid-July the hawks attacked martin fledglings near our colonies and usually scored a kill, often several. Since I am retired, observant and vigilant around our martin colonies, I witnessed numerous visits and direct attacks by resident Cooper?s hawks. I observed the same predatory behavior at my previous martin colonies in north Florida.

In 2006, our martin colonies will surely experience the same or possibly greater predation pressure as we endured in 2005 from migratory Accipiters, merlins and peregrine falcons from February through mid-May, with April being the most dangerous month. Our area in northwest Louisiana is apparently a major migratory flyway for raptors and songbirds and I often observed multiple visits/attacks by various Accipiters and falcons in a single day.

The resident Cooper?s hawks will no doubt make an appearance when the first martin fledglings leave their nests to face the dangers of the natural world. This coincides with the breeding cycle of the Cooper?s hawks which will have nestlings or fledglings at that time. Since I anticipate an even larger number of martin fledglings with more pairs nesting in 2006, the hawks will concentrate on this vulnerable prey. Having a huge biomass of martin fledglings saturating the immediate area will greatly minimize predation on the adult martins by hawks. This scenario is much better for our colonies because of the reduced chances that parent martins with nestlings will be predated. I believe it is better for a fledgling to be loss to predation than a parent martin which could adversely impact a brood of nestlings. Mortality is high for martin fledglings and predation is just one factor in this natural process that has existed since time began.

Steve Kroenke

[rickluc]

Would a scarecrow work? I have an electric santa clause that waves his arms? Could a person dress him up?

[Steve Kroenke]

Hey,

Scarecrows probably would have limited impact on discouraging Cooper's hawks attacks, particularly in the long term. I have tried them in the past. I even dressed in a certain way and wore my favorite cowboy hat. Then I created a scarecrow with my hat and the same clothes. It worked for a few days and then failed even though I moved the scarecrow around my yard. Perhaps an animated scarecrow with moveable arms would be more effective for a short while.

However, many of the Cooper's hawk attacks on the martin fledglings occur several hundred yards from the colonies, so a scarecrow would not work in those cases.

The best defense at the colony is to have a completely open site where the martins can see approaching danger. We have that. Also vigilance by the landlord can sometimes prevent direct attacks inside the colony. And using realistic martin decoys may help deflect a hawk from attacking the real thing for a short while. But attacks outside the perimeter of the colony are almost impossible to stop.

Thanks for sharing your idea.

Steve

[John Miller]

Maybe if Steve lent his cowboy hat for the Santa with waving arms.... (it might scare me)

Seriously, I dread the day Cooper's Hawks find my new small colony in a park in St. Louis, but it's in a very open site.

The martins have departed the houses , and I'm just now seeing a few Cooper's Hawks in the park and in my nearby neighborhood, which is an inner metro area of older small brick homes. Yesterday morning, my cat was looking up in a big pin oak in my front yard, making a chattering noise with his mouth that cats make when they see a particularly intriguing bird they can't reach, and there sat a Cooper, eyeing a neighbor's bird feeder in the next front yard. I walked out and clapped my hands -- as Steve has suggested -- standing not 20 feet below -- and he continued to sit there, unimpressed with me. As my neighbor mostly feeds sparrows, I went on a ran some errands and let them all be.

John Miller,
St. Louis, Mo

[geneinmurphy]

Steve.........PM's nornmally return to a site the next year if they successfully raise their young there the current year. For the ASY's that lose any of their fledglings, do you think this will discourage them from returning the next year and instead go to another site due to a high level of hawk attacks experienced at the old site???????

[Steve Kroenke]

Hey John,

I have seen very tame Cooper?s hawks in downtown Tallahassee, Florida near my previous office building. These hawks were unafraid of people and I could observe their hunting tactics up close. In fact, I could watch them catch birds and pluck them with me standing close by. These are no longer ?rare forest hawks? in many areas and their numbers are increasing and expanding into both suburban and urban locations. I have read where Cooper?s hawks were found nesting on the campus of the University of Miami in sub-tropical southern Florida! The bird books need to be re-written!

Here is a link to an article about a Wisconsin town that may have the largest density of Cooper?s hawks in the country. The professor who studies them believes Cooper?s hawks may be one of the most common raptors around.

http://www.pcgazette.com/outdoors/feb00/waw2-25.htm

Almost any size martin colony can attract Accipiters though larger ones have more activity and associated martin vocalizations. Of course, hawks are attracted to these larger prey concentrations. Similar to an African waterhole attracting not only herbivores but carnivores like lions.

Open colony sites are much better than tree encroached ones, but these hawks can still predate martins in both locations.

I believe Accipiters have learned to associate martin housing with food and are now actively seeking out colonies during migration and on their nesting grounds. This situation will continue to grow in intensity as they hawks continue to increase in population and expand their breeding range.

Steve

Hey Gene,

Since the martin parents were able to fledge their young and most did survive, this Cooper's hawk predation would not, in my opinion, adversely impact the return of the martins next season. Martins are faced with predation pressure every year on both their breeding and wintering grounds. So they are conditioned to "deal with" unless it gets out of control. Many martin fledglings don't survive their first few days out of the nest.

Now if the hawks (and/or owls) could have succeeded in destroying the martin nests at the colony and killing most of the nestlings, then this may signal to the parent martins that this site is unsafe. When martins experience significant reproductive failure via predation directly at the colony, then the surviving martins instinctively recognize that this area is possibly unsafe.

The key is the amount of predation and where it occurs. Predation directly at the colony where many adult martins and their young are killed at the nests has the greatest adverse impact and may cause a colony to be abandoned. Predation on the fledglings in particular away from the colony site or as they are flying about near their nests has a more limited impact and the parent martins probably would not "correlate" that with a possible problem at the nests. This kind of predation is "more normal" and happens all the time at many colonies though the landlords may never observe it.

Just some of my thoughts on the subject.

Steve

[graue]

This year I have lost several martins to hawks. One even lit on the martin house and tried to reach into a compartment. My house has deep compartments and so it was not successful but the hawk kept trying until I chased it away. All during June and July the hawk visited daily. I could tell when it was near by the actions of the martins. When I saw it I would run out in the yard and clap my hands and that would scare it away for a while.

[Steve Kroenke]

Graue,

I am amazed at how Cooper's hawks have increased in numbers and expanded their nesting ranges. In the past, these hawks were only recorded in the northern and occasionally central parts of Florida. Now, these hawks are moving south and can be found all over the state. Several years ago I visited Key West, Florida and guess what I saw! Yes, a Cooper's hawk! These hawks are common in north Florida where I previously lived and they heavily predated my martin colonies.

I have had correspondence with a number of landlords who have experienced Cooper's hawk predation on their martin colonies, both small and large. These hawks are doing well and many are learning to predate martin colonies.

The deep cavities will help protect the nestlings, but the adult martins may still bolt from them when the hawk is either sitting or hanging on the house.

I have watched Cooper's hawk sit on gourd crossbars and houses and chase any martins that fly out. These hawks will also fly toward a gourd rack or house and try to flush martins out.

Your vigilance and protection method surely saved many of your martins. Good luck in the future.

Steve