Blog #355 Autumn Means Migration for Ospreys!

Juvenile Osprey playing at Salt Point just before migrating, courtesy of Karel and Cindy Sedlacek. 

Autumn in the Eastern U.S. is a restless time of year for wildlife and especially birds.  Reports of incredible endurance and distances traveled during wildlife migrations range  monarch butterflies, elk, humpback whales, American eels, Atlantic salmon, menhaden,  and striped bass. Birds are famous for their migration feats and global travels, notably  shorebirds like the Bar-tailed Godwit, Red Knot, and Artic Tern, and long-distant raptors  such as Broad-winged, Sharp-shinned, and Red-tailed Hawk, and the Osprey.

Lilibit, calmly sitting, prior to her being overcome with zugunruhe, courtesy of Karel and Cindy Sedlacek. 

In autumn, migratory birds and other animals succumb to zugunruhe, a German word  describing the intense “migratory restlessness period.” Zugunruhe is the internal cue that  signals seasonal migrations; it causes the uncontrollable urge to move and travel  thousands of miles, past hungry predators, strong winds, food shortages, and stormy  weather to get to the safety of their winter home in the tropics.  

As soon as the Osprey fledglings learn to fly and capture food, they are considered  juveniles and ready for migration to the wintering homes in South America, as far south as  Brazil. Some birds migrate in families. The enormous flocks of migrating Canada geese can be composed of this year’s brood and their parents or all yearlings from the year  before. Osprey young, by contrast, migrate entirely on their own without prior knowledge  of the route. How Osprey juveniles know where to go and how to get there is one of  greatest migration mysteries. 

The roles of the adult Ospreys change during the breeding season. During most of the  breeding season, the mothers, like Salt Point’s Ophelia, do the majority of tending to the  eggs and young. Orpheus’s role as the father is to supply fish to the family, the amount  increasing during the season as the offspring grow. The parental roles change according  to the needs of the young. Ophelia and the other mothers leave the nest once their young  start learning to fish. She will spend the next few weeks gaining weight that was lost 

during the nesting period, as mothers often subsist on leftovers. Osprey expert Alan Poole suspects that Osprey mothers are probably hungry much of the time they are rearing their  young, especially as the young get older and hungrier. Most mothers leave on their  traditional routes south to the Caribbean and South America by mid-August. 

Father Ospreys like Orpheus continue bringing food to their nests until the youngsters become capable hunters. According to Poole, the father’s role is to transform the fledgling  Ospreys into independent juveniles. By mid-September, most Osprey parents will have  departed the nest and surrounding area, followed by the offspring. However, many fathers  continue to fish for their young until the juveniles leave the area. Juveniles may also  explore the area for hundreds of miles before beginning migration. 

Rosie flying about Salt Point before her departure in September, courtesy of Karel and Cindy Sedlacek. 

September finds the juvenile Osprey building up their energy stores as they perfect their  flight and hunting prior to leaving. Suddenly, each juvenile will be individually flooded with  zugunruhe and the young bird will take to the sky. Flying on a course that will reveal itself  in time, the juvie performs this momentous journey to a place they have never been and  do so without any help from other Ospreys. The Osprey, young and old travel individually,  however, several may be seen together at a fishing hole along the migration route or in  the same thermal en route. 

First time migrants tend to fly too far east or west and have to course correct. Over the  years, the route becomes more uniform and hugging the coast. See the map below of the  2016 fall migration of the Osprey Wausau flying with a GPS tracking device.

Fall migration route of Wausau (male, aqua) from NH to Colombia in 31 days.  

Other colors represent other Osprey, map courtesy of Dr. Rob Bierregaard. 

While no one knows exactly how juvenile Ospreys navigate there are many theories.  Ospreys mounted with satellite transmitters have revealed the general flight path used  along the Atlantic coast. Young Ospreys are likely guided by the sun and stars, and the  topography and air currents along coastline of North American to the tip of Florida, then  cross the Straits of Florida to Cuba before heading east to Haiti and the Dominican  Republic. From there, juvenile Ospreys will usually fly 500 miles over open water to winter  in northern South America, in places along rainforest rivers and lakes into the Amazon  Basin ranging from Venezuela to Brazil. It's more than a 3,500 mile journey, perhaps as  much as 5,000 miles depending on which route a particular young Osprey may take. They will then typically spend 18 months in South America before making their first return  migration northward to find a partner, nest, and raise of family of their own.  

There are many dangers during first-time fall migrations. They can get hit by a car,  tangled up in power lines, or shot at by an angry aquaculture farmer in the Caribbean or  South America. Ospreys are easily blown off course by storms and hurricanes, and can  get lost when crossing the open ocean. The good news is that statistically those young  Ospreys that do survive their first year have a good chance of surviving future migrations. 

Read some of my other blogs on the fall migration includinging Blog #57 Wired Up and  Winging Down the Flyway (2014); Blog #55 Watching Osprey Migrating at Hawk Mountain (2014); and Blog #145 On the Road Again (2016); #215: Godspeed and #214:  Zugunruhe, (2018).

Eyes to the sky! 

Candace 

Candace E. Cornell 

Friends of SaltPoint 

Lansing, NY 

Cayuga Lake Osprey Network 

NY cec222@gmail.com 

Guest Photographers: 

Karel, a Senior Data Analyst, and Cindy Sedlacek (aka BOGette), a Director of Data Administration and Reporting, are long term Cornell University employees. (BOGette stands for Birder on the Ground). They were introduced into the wonderful world of  raptors after watching the 2012 Lab of Ornithology's Bird Cams -- BigRed and Ezra and  Stanley and Iris. Since that introduction they have spent their free time documenting the lives of local Red-tailed Hawks and Ospreys via livestreaming and photography — https://livestream.com/karelsedlacek —at Cornell and Syracuse Universities. 

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