On May 12 and 14, two rare white-naped cranes hatched at the Smithsonian Conservation Biology Institute in Front Royal, Virginia.
The biological parents of this year’s two chicks are named Amanda and James. Amanda and James imprinted on people as chicks and had not bred successfully before they arrived at SCBI. However, Amanda was already paired with a crane named Alex. Since cranes mate for life, we would not separate the established pair. Instead we used artificial insemination to breed Amanda and James. Since Amanda and Alex had never raised chicks before, we left them with one fertile egg and gave the second fertile egg to a more experienced pair of cranes named Abigail and Ray.
This year’s hatches bring SCBI’s white-naped crane flock to 12 birds which is 20 percent of the entire captive flock in North America. SCBI has also produced seven chicks in the last five years, which is the most production of any zoo. All of those chicks came from adults other zoos were unable to breed.
|Foraging in the grass|
Cranes are omnivorous, meaning they eat both animal and vegetable matter. Their varied diet includes small mammals, reptiles, amphibians, insects, worms, plants, tubers, and seeds. The main diet we provide our cranes is a pelleted food that is specifically formulated to meet all of their nutritional requirements.
Normally cranes are very skittish and would become nervous and/or move away from anyone observing them. However, we furnish our birds some special food items, or treats, which draws them closer for a more thorough assessment of their appearance and behavior. Closely monitoring the health of our birds ensures the best care for our captive charges. Offering treats was an essential part of getting our crane chicks, Cal and Bill, more comfortable with their keepers. The treats we offer our cranes include dead mice, grapes, and mealworms, but everyone’s favorites are the mice.
When Cal and Bill were young they would each make a chirping call to beg their parents for food. The parents responded by holding a food item in their bill in front of the chick so the chick could take it from them. Cranes do not regurgitate food for their chicks like other birds. Instead they give the chicks small pieces of food to eat whole.
Cal and Bill are frequently seen alongside their parents searching their enclosure for natural prey items. We manage their habitat to resemble their natural environments which subsequently provides them with natural prey items.
|A muddy bill from foraging.|
We primarily manage their habitat by mowing and keeping the grass at varying heights. Mowed pathways of shorter grass enable the cranes to walk easier and provide nice resting spots for them. Leaving areas of longer grass concentrates prey such as insects and rodents and gives cranes the opportunity to naturally forage for food. Each crane pen has a butterfly bush to attract butterflies and moths for the cranes to catch and eat. There is also a small stream that goes through each pen which provides them with the occasional crayfish or frog.
The primary prey our cranes find are invertebrates. White-naped cranes frequently probe into the ground with their stout pointed bills in search of invertebrates. Their digging activities are evidenced by areas of freshly dug up dirt throughout their enclosures. Upon closer look, amongst the bare dirt are holes the cranes have dug into the ground in search of food. Because of this foraging technique, Cal and Bill often have dirt and mud all over their bills.
|The chicks' changing plumage|
Feathers give birds thermal insulation and the ability to fly. Birds spend a lot of time maintaining their feathers by preening, which is the process of arranging and cleaning feathers with their bills. Over time their feathers get worn or damaged and need replacing. Adult cranes molt, or grow new feathers in to replace older feathers, once a year. Molting requires a lot of energy from the birds as the shafts of growing feathers are supplied with blood. The molt is therefore timed to occur at the less physically demanding time between the end of breeding season and the start of migration. The timing of their molt also coincides with the time period just before their chicks being able to fly, so an entire crane family will be flightless for the same short period of time.
When Cal and Bill hatched back in May they were covered in short, tan downy feathers which gave them a soft and fuzzy appearance. Within a few months, these same feathers had grown longer making the chicks look less fuzzy. The new feather growth was gray so by late summer both crane chicks now have a predominantly gray plumage. They still have some tan coloring on their heads, necks, and wing feathers. The tan coloring on the ends of their feathers will remain until they go through their first molt next year.
|The chicks' primary flight feathers|
At two months old, both Cal and Bill had fledged. This means their wing feathers had grown long enough for them to fly. In the wild they would now be able to join their parents on short trips to find food and safe resting spots. Our spacious crane enclosures at SCBI do not have roofs to prevent cranes from flying out of their enclosure. The lack of a roof allows for tall trees to grow and gives our cranes much-needed shade in the hot summertime. In order to keep our cranes from flying out of their pens we clip their primary flight feathers each year. Primary feathers are the long black feathers at the end of each wing. Once Cal and Bill’s primary feathers started growing in we began trimming them every few weeks. Cranes can still fly short distances without primary feathers so we only trim the primary feathers on one wing. This keeps them off balance enough to discourage actual flight. In the wild, both Cal and Bill would soon be preparing to migrate south for the winter with their parents.
As adults, male cranes are a bit taller than females and have slightly different displays and vocalizations. But as chicks, males and females look and act the same. Unlike mammals, bird genitalia are internal so it’s difficult to determine their sex. To determine the sex of this year’s chicks, a small blood sample was taken from each chick for DNA analysis. The results came in, and both chicks are boys! The previous five chicks born at SCBI were all females which helped even out a previous imbalance; there were more males than females in the captive population.
Both chicks weighed around 120 grams when they hatched in May. Crane chicks grow very fast and can gain as much as an inch in height per day. By mid-June the chicks weighed around two kilograms. By August both were nearly as tall as their five-foot parents.
Although the brothers look the same, the two chicks behave differently because they are being raised by different pairs of adults. The older chick, named Cal, is much calmer, an attitude he learned from his calm and experienced foster parents, Abigail and Ray. When their keeper is within view, Cal stands his ground next to his watchful parents and observes the keeper intently. Abigail and Ray are not alarmed by the keeper’s presence as long as he or she doesn’t approach Cal.
The younger chick, Bill, is more skittish reflecting the more anxious behavior of his first time-parents, Alex and Amanda. Alex and Amanda make threat displays and vocalizations even if the keeper has not entered their territory. Bill responds to their alarm by trying to hide. Keepers are gradually earning the trust of this trio by caring for them in a calm and predictable manner as well as offering them delicious mice.
|A one-day old chick, being raised by Abigail and Ray.|
Amanda and Alex are raising a chick for the first time. It takes both members of a crane pair working together to successfully incubate eggs and raise chicks. Alex took to parenting right away, immediately staying near the chick and always feeding it before eating his own meal. Amanda took a few days to begin feeding the chick but was always there to brood (sit upon and protect) the chick during rainstorms and to defend the chick.
Cranes are very protective of their chicks, even toward keepers they know well and are accustomed to having around. Amanda constantly threatens the keepers with displays and vocalizations, while Alex stands with the chick on high alert. Whenever a keeper enters this pair’s territory, Amanda keeps a very close eye on her uninvited visitor. Wherever the keeper goes Amanda will follow right alongside or behind, “escorting” the keeper around. As the keeper leaves, Amanda and Alex always let out a loud bugle-like call, known as a “unison” call, to announce their territory and likely celebrate another vanquished foe.
Abigail and Ray are doing an excellent job raising the second chick. This pair has raised five other chicks, so they are very skilled at parenting. Abigail and Ray had produced infertile eggs this year so we simply switched their infertile eggs with Amanda’s fertile egg. The cranes accepted Amanda’s egg because it looked identical to their own. We even had this surrogate pair do most of the 32 day incubation of both of Amanda’s eggs due to their experience. Amanda and Alex were provided realistic looking plaster “dummy” eggs to incubate.
Once the real eggs were close to hatching one was returned to the new parents for them to hatch and raise. Abigail stays close to the chicks whenever a perceived threat approaches. Ray takes the lead in defending the chick by making threat displays and always keeping himself between the chick and the keepers. Ray is quite enthusiastic in defending his chick and territory even chasing off wild rabbits that dare graze in his family’s habitat.