Eggs to Flight
Watching Osprey Mature
The following slide show is a photoessay depicting the maturation process of an osprey from egg to fledgling, as photographed by a licensed permit-holder supervised by the NJ Division of Fish and Wildlife, Endangered and Nongame Species Program and under the direction of a Principal Wildlife Biologist. The purpose of the show is for public education and use by banders as an aging tool.
Please note that disturbance of osprey without such supervision is prohibited by law.
This is a mature osprey with nearly mature nestlings. The slide show will offer us a window into the week-by-week growth of osprey nestlings. It is intended to give you a glimpse of their development and some of the perils that wild creatures face. It should also prove to be a useful tool in helping osprey banders to age chicks.
This nest is on the Maurice River south of the City of Millville. Citizens United to Protect the Maurice River and Its Tributaries, Inc. is the steward of this nest, which is called Meadowview and was erected in 1985. On 5/17/03 we used a mirror to check the status of the nest, and three eggs were observed. Egg data for the previous 10 years at this nest site are as follows; 1993 - 2 eggs, 1994-96 - 3 eggs, 1997 - 1 egg, 1998 - 2 eggs, and 1999-2002 - 3 eggs. (Because this was a difficult angle to capture in a mirror we used a CU file photo here; aside from this one, all shots will be current unless otherwise noted).
Normally the osprey lays three eggs, although in 2001 the Vanaman nest had four. Since 1994 we have banded 153 clutches; of these only ten have had four eggs and only three of those actually produced four chicks. Thus far, for 2003, only one nest has had four eggs. This photo enables you to see their eggs and coloration more closely.
Newborn Osprey Chicks
Meadowview Nest 5/17/03; note unhatched egg and white egg tooth on chicks’ upper beak. It will be interesting to see whether the third egg hatches. The hatchlings are likely one and two days old. Chicks' development is semialtricial at birth: immobile, downy, eyes open and fed by an adult. Osprey normally begin to incubate after the laying of the first egg so the eggs will hatch consecutively (asynchronous hatching) instead of all at one time. Osprey on the Maurice generally hatch earlier than the Atlantic Coast birds. We suspect this is related to the early herring run.
Osprey Chicks-1 Week Old
During a break in the weather on 5/24/03 we get a peek at the chicks. Hip, hip, hooray! the third egg has hatched. The chick facing the camera is the youngest as is evidenced by its larger beak tooth (the white area on the end of the beak) but its smaller size is hardly discernable. This chick probably hatched on 5/17/03.
If food is plentiful there is a good chance that all three chicks will survive. Many perils could await this naive threesome. If food is scarce the chicks will be taken care of on a priority basis. The strongest and healthiest has the best chance of survival. Well-fed chicks rarely fight, yet siblicide is not uncommon in osprey. It is not advisable to intercede with nature's course so prepare for what could be a smooth sail or an emotional roller coaster. We will discuss various potential dangers later.
Two Weeks Old 5/31/03
Being born last has its disadvantages; by the end of the second week the third chick is markedly smaller than its siblings. Even though they were likely born on three consecutive days there is less of a size difference between chick one and two than between chick two and three. Note the enlarged crop on the chick near the ruler; certainly it was well fed. The chicks have doubled and nearly tripled in size in one week. Biologists find the greatest energy demand is between week 2-3. Instances of mortality on the Atlantic Coast are normally highest during this period; thus biologists deduce that food shortages are the root cause.
Note the following natural defense mechanisms: The chicks are well camouflaged; their light stripe resembles the top of a stick and their dark sides look like the shaded area. In last week’s slide two chicks (probably 8 & 9 days old) had already learned to lie low - a defense from aerial predation. This week all three chicks assume this posture as the mother sounds a warning call.
Nest Design/ Mother Lifting-Off
The nesting platform adds a layer of man-made defenses to the natural defenses discussed on the previous slide. The predator guard (coned-shaped metal below cross members) at the bottom prevents raccoons and snakes from entering the nest. Osprey often build on electric poles which have the obvious potential for electrocution which the platform does not share. Our nest is "Y" shaped to help osprey imprint to crooks in trees when seeking a natural nest. The "Y" is also designed with the arms projecting over the nest so the adult birds can assume a threatening position above the young as a deterrent to aerial predation (owl attacks). Lastly our platforms are less likely to collapse, although these birds have been over-zealous builders so we are concerned with possible instability due the sheer mass they’ve added to the nest this year.
Three Weeks Old - 6/7/03
With the chicks' backs to us we can observe their rapid development. Although they were probably born on consecutive days we see varying degrees of both girth and feather growth. The chick lying on the left is clearly the oldest.
On June 8 we banded two chicks at the Sweetmeadow platform; they were about 5 1/2 weeks old! Each year since 1996 Sweetmeadow has been ahead of the other nests in producing young. There is such a wide range among our local birds that some of the nests on the river still have unhatched eggs. Our subject nest for this essay normally runs earlier than other nests by about 2 weeks.
An osprey’s diet consists of 99% fish. There are very few records of any other prey source although osprey in Florida have been known to capture and eat juvenile alligators.
Four Weeks Old- 6/14/03
Once again we have lined up the chicks left to right: oldest to youngest. The young birds are now beginning to outgrow our ruler. The smallest is about 11 1/2 inches long and the oldest an inch to an inch and a half larger. Their orange iris will turn to bright yellow when they are mature. This change is believed to be linked to hormonal changes.
In the closeup we get a unique look at what is referred to as the nictitating membrane. This is a clear covering, in addition to the upper and lower lids, which moves across the eye for moisture, cleansing, and protection in times of struggle. It can be closed over the eye without interfering with vision.
Four Week Old Chicks Are Banded
A cloth is placed over the heads of the chicks so that they remain calm, enabling the bander to work with greater efficiency. Falconers use a hood for the same purpose.
Here we see the bander’s hand holding the tarsal so as to expose the band. The talons are uniquely designed to grasp fish. The bottom of the feet and toes are covered with short sharp spines to aid in holding this wet prey. An additional adaptation allows osprey to turn their outer toe backward with parrot-like dexterity. They are the only raptor whose front talons turn backward. (A. Poole / D. Dobkin)
Check out "Fish and Chicks...The Story of the Maurice River Osprey" for more information on osprey and more information about the applications of banding.
On June 29, 2003 we recovered a dead eight-year-old osprey in a nest just across the river from Bricksboro, NJ (remnant village south of Port Elizabeth). We reported the band number to the U.S. Geological Survey. When an individual turns in a band to the North American Bird Banding Program through the USGS they receive a certificate. Interestingly, the bander who discovered the bird, Jane Morton Galetto, knows the original bander; Ted Nichols. Ted is the same NJ DEP, Division of Fish and Wildlife biologist who has been doing the canada goose studies on the Maurice River. Reading the Certificate of Appreciation will explain the benefits of reporting banded birds.
Check out "Fish and Chicks...The Story of the Maurice River Osprey" for more information on osprey and more information about the applications of banding.
To see a large image, download the PDF.
Five Weeks Old - Meadowview Nest
The photo of three in a row isn’t happening! Once moved, the youngest and feistiest has elected not to listen to its mother’s distress call, and refuses to lie low. The moment the chicks’ heads are uncovered one chick’s “teen- aged spirit” is unveiled. His uncooperative attitude does give us a glimpse at raptor’s eyes, which are situated on the front of the skull for hunting. By contrast prey species like songbirds have eyes more strategically situated on the sides of their head, making them more aware of attackers.
Even with necks somewhat retracted the chicks are about 15” long. Just last week they were approximately 11 1/2” long and starting to outgrow our ruler.
A Harsh Spring Causes Failures in Many Other Maurice River Nests
Although our subject nest has thus far escaped tragedy, many others in our river system are not doing as well. The cold rainy spring (2003) has had dramatically negative impacts on the osprey population. We have discovered nests with extreme variations in size and vigor among siblings, with one chick likely starved to death discovered with two healthy chicks. Many nests that had eggs were abandoned and empty. In these photos of two other nests, we see a runt with its much healthier sibling, and then two robust chicks (12”) with their starved nest mate. Often a runt is killed by the stronger, but in this case interestingly there are no signs of hostility, simply of starvation (as evidenced by a protruding breast bone and sunken abdomen). Last year we banded 60 chicks; this year the best case scenario will be about 35.
6 Weeks Old 6/28/03
The Meadowview nestlings continue to do well. The runt has shorter tail feathers and measures 14”.
In the close-up we see a mosquito attaching to the outer corner of the osprey’s eye. West Nile is a mosquito-borne avian disease. Biologists don’t know how vulnerable osprey are to this often fatal ailment.
Don’t Ruffle My Feathers!
Displaying ruffled feathers is a defense mechanism that enables the chick to look larger and more aggressive. If that doesn’t do the trick, they can spread the wings for the fully-fledged look. The plumage on young osprey differs from adults’ in a number of ways. Each of the dark back and wing feathers is variegated with light tips, the crest is a tawny shade versus a predominantly white cap, and the chests have more flecks of brown than the adults. Mature females tend to have a speckled collar where the male is more uniformly white.
7 Weeks Old 7/5/03
This should be our last trip to the nest’s edge. One chick still responds by lying low but the other two have nearly developed the ultimate defense mechanism - FLIGHT! The breeze on this day is barely discernible, yet they have already learned to face the wind and raise their wings for lift. Perched birds often use this position to allow a fast escape.
We now approach the most precarious of times for the full-grown osprey; it’s fly or die, and flying is hazardous. The greatest mortality takes place in the first year of life. Taking off, landing and hunting are all difficult. These young birds have already begun to preen their feathers for their solo experience. If you look closely you might be able to make out the downy feathers that litter the nest. Also notice they are especially long-legged for grasping fish just below the surface of the water.
The Nictitating Membrane at 7 Weeks
Raptors, meat-eating birds, are very dependent on acute eyesight for hunting. The nictitating membrane now appears much clearer, enabling the bird to see through it more distinctly in times of struggle. Eyes are finely crafted for the hunt. A rather flattened lens placed further from the retina produces a longer focal length that creates a larger, more telescopic image. A curved cornea and large pupils admit lots of light to further enhance imaging. Raptors are said to have eyesight which is sharp at three times the distance of the human eye.
Keeping It Clean
Osprey do not foul their nest. Whitewash is excreted overboard by the posture caught through the lens of this telescope. What a wonderful display of bloomers! This same posture is used by the female during mating.
Is It Time to Eat Yet?
In their 7th week we see an attentive mother feeding a chick. Note: the dark back and wing feathers of the adult female versus the chick’s lightly tipped feathers. It takes as much as six pounds of fish a day to feed this family of three. The male will deliver the majority of the daily catch. The harsh reality of having to fend for themselves is about to take place. Feedings will become less frequent and the mother will encourage the young to leave the nest. Vocalized begging will become incessant.
8 Weeks Old
This picture illustrates three different stages of maturation toward flight. The juvenile on the perch has already fledged. Nestled in the middle and not yet ready to attempt flying is likely the youngest chick. Leaping about and hoping for a maiden voyage is the second oldest osprey. Their progression appears to be spaced three days apart.
A number of days are spent exercising the wings, experimenting with lift and leaping about before fledging.
The Stall or "Packin’ a Lunch"
The male displays a magnificent stall while delivering a breakfast to the family. Likewise the female is capable of stopping on a dime as she perches above the nest. The young birds are often not as capable during their first flights and failing to stall before perching can leave them inverted like bats in trees.
Placing an Order
Begging for some of mom’s meal allows us to peek at the difference between the adult (yellow) and juvenile (orange) irises. In week seven the adolescents feed themselves and are also fed by the mother.
This young osprey shows off its first flights to its nested siblings. After each of these displays the second in line becomes extremely active. With the grace of a ballerina the osprey poses, seemingly on tiptoes. It fails to accomplish any forward motion but does float gracefully above the nest.
Not surprisingly, birds are uniquely adapted to flight. Predominately hollow bones, a complex respiratory system, strong chest muscles, and feathers aid flight. The hollows in certain bones are an integral part of the respiratory system.
Preening, Preening and More Preening
Preening feathers is an important activity. Birds rub their bill against an oily sac at the base of the upper tail feathers, called a “preen gland,” and distribute oil over their feathers. They adjust the feathers for flight and oil them for insulation. Oily feathers are especially beneficial for birds who have considerable contact with water. Scratching near the ears is believed to be performed for further spreading of oil and removing parasites where their beak will not reach.
9 Weeks Old 7/19/03 - All Chicks Have Fledged
After hours of observation it appears that the nest is never left vacant. Sleeping, eating, perching, and preening make up the daily activity. During all of the observations a dutiful male, when not hunting, perches primarily in trees on a coastal bluff about 100-150 yards away. Being unable to distinguish one chick from another makes it difficult to know if all have fledged, until at 8 1/2 weeks a remaining chick exposes muddy wet legs, divulging that he too has joined his siblings in flight.
Food is a Valued Resource
Post-fledging the nest remains home-base till migration to South America. The adults continue to deliver food to their young. At dinnertime three fish were delivered in less than an hour. Chicks feed themselves but have not been observed to be hunting. Throughout the observation period if flushed during mealtime the adults always take their quarry with them. The moment the disturbance is removed to the same safe distance the adult returns to its role as provider. Here we see a chick unsuccessfully attempting to take the entire meal from its mother. No disturbance during the eighth week caused all the chicks to flush. But those that do follow the adult’s lead, taking their unfinished prey with them.
Class is in Session
Chicks learn many behaviors from their adult counterparts. The male, who has rarely delivered sticks in recent weeks, spends the mornings of week 8 1/2 showing off his contribution to nest building. He delivers twigs and branches and the female weaves them into place.
Pre-copulation activity has not escaped this chick’s power of observation; here he is seen mounting an unwilling mother.
Near the end of week 7 the male bathed repeatedly around the nesting platform. One couldn’t help but wonder if the one chick who had been whitewashed by a sibling was expected to accept the hint and follow suit.
Although osprey rarely regurgitate (spit out indigestible matter), we did witness one occurrence, in which fish scales appeared to be spewed from a chick. This was accompanied by rapid shaking of its head.
Don’t Count Your Chicks Before They Hatch
This nest’s story seems to have a happy ending. Unfortunately, this year proved to be the most perilous breading season since we began our Maurice River Osprey Colony Project in 1985. With 30 active nests and an egg count of 64-71, just 33 of an anticipated 60+ chicks have survived. Only one other pair produced 3 chicks, compared to 2002 in which twelve nests produced 3 chicks each. (Click here for osprey statistics) The dangers for these young osprey have just begun. Studies show that only 50% of raptors survive their first year after fledging. Migration is risky business. During the last week of August and first few weeks of September most of the NJ Delaware Bayshore osprey will begin their annual migration to South America. In 2001, by August 23 a productive adult female outfitted with a satellite transmitter was already in VA; five days later she was in Cuba, by the middle of September she was in Venezuela, and then a transmission from her wintering grounds in Manaus, Brazil was received on October 1st.
This young family has been given a hearty start by two diligent parents whose competence during this breeding season outmatched the vast majority of their adult peers. One can only guess what wondrous adventures await this young winged trio. Thank you for permitting us share their story with you.
A special thank you to NJ DEP, Division of Fish and Wildlife, Endangered and Nongame Species Principal Zoologist Kathy Clark who not only helped on this project but is a brethren of the muddy boots. Kathy coordinates management of New Jersey’s entire osprey colony of 350+ pairs and growing.
Thanks also go to the following:
Peter Galetto, with his tag team Hobnob & Jersey, who dutifully captains, bands, mirrors, and constructs platforms and blinds. And by the way, in addition to his other many talents he swings a fast ladder. Without his participation this slide show would not have been possible.
My faithful editor and proofreader Leslie Ficcaglia who also volunteers countless hours not only on text but as an osprey steward.
Travis Vertolli whose teenaged body braved waking at an early hour to assist in canvassing a photo blind.
Ken Walker for his photo expertise and generosity.
Kevin Karlson who has provided a number of avian photographs to Citizens United; we are grateful for his kindness and have included with each an acknowledgment and copyright.
A thousand thanks to the hundreds of volunteers who over the years have had a hand in constructing, erecting and observing the platforms of the Maurice River.
Finally we are forever indebted to the National Park Service’s Wild and Scenic River Partnership Grants Program which enables us to do so many wonderful projects including but not limited to educational aspects of the Citizens United to Protect the Maurice River and Its Tributaries, Inc. website.
Many Thanks - Credits
Photos and Narrative by Jane Morton Galetto