Milestones

Birds have developmental ‘milestones’ just like humans. Right now there are so many Bald Eagle nests where eaglets are already two or four weeks old. In others, the parents are incubating eggs. And there are others where the parents are only beginning to start working on the nests. You can see every stage of a Bald Eagles growth from the female laying the egg to their fledging from the nest on the many streaming eagle cameras. Every eaglet is different, just like people and their development will not happen on a single specific date.

Within the overall umbrella of bird development, you might remember Daisy the Duck (see previous blogs for more information on this remarkable little duck). This Black Pacific Duck laid her eggs in the Sea Eagles nest. We knew that the ducklings would jump from the nest 24 hours after hatching if we actually got to hatch – which, sadly, we did not. Those ducklings could see, forage, swim, and take care of themselves without help from the parent. Daisy would, still, gather them up and protect them during the night. Fully independent of their mother, those ducklings would have been ‘precocial’. In contrast, the eaglets are not fully developed, nor are they able to feed themselves, or fly down from their nest. Indeed, they are covered with fluffy down but are unable to regulate their temperature.

It takes from ten to thirteen weeks for eaglets to fledge whereas the ducklings do this at twenty-four hours. Eagles as well as all other hawks or raptors are ‘semi-altricial’. This means that they will be dependent on their parents for everything they need until fledge. Even after fledging, the parents will teach them to hunt and will provide prey supplements for them.

Until the onset of streaming cams, there was very little quantitative information on the development of Bald Eagle Nestlings. Today, there are cameras, often more than one, on nests around the world. You can, at any time of the day, watch Bald Eagles, Peregrine Falcons, Golden Eagles etc. at your leisure. The growing community of citizen birders has impacted the knowledge of avian development and behaviour considerably. We are, indeed, continuing to learn every day. Advances in satellite transmitters means that birds can now be studied after leaving the nest providing much information about foraging, distance from natal nest to establishing their own territory, etc. This blog today is general and non-scientific in its terminology.

Many look at the development of Bald Eagles through three stages: structural growth, feather growth; and behavioural growth. Others attempt to combine feather growth with behaviour and structural development into weekly goals. In fact, I have pondered over this blog and how to approach it for several days because there are different factors that impact development. One of those is gender. There are also studies that have shown that the levels of salt in the diet impact growth while others have examined the amount and quality of prey. We know from studying Red Tail Hawks that if you double the amount of prey and the eyases remain in the nest for several days beyond the average, they are better equipped to fly and hunt. Their overall condition is much stronger. For the purposes of our discussion, I have used evidence from the NEFL Bald Eagle nest in 2021 and the SWFL Bald Eagle nest in 2021 and 2017 (E9). There is one eaglet on the NE nest and two on the SW nest in 2021. The parents on the NE Florida nest are Samson and Gabrielle. Samson was born on this nest on 23 December 2013. He is a little over seven years old. We do not know the age of Gabrielle. At the SW nest, Harriet is in her mid-twenties and M15 is 11 years old. Both nests are located within close proximity to a city – Fort Myers and St Augustine. The Fort Myers nest is unique in that the D Pritchett family has a working farm on the land where the nest is located. They also stock a pond in close proximity to the nest specifically for the eagles. This means that there is always food available. Still, the parents bring in road kill as well as fish from the pond. The NE nest does not have this advantage but nest observations reveal that there is an abundance of food although the variety might not be the same as the SW nest.

Both E17 and E18 were born on 23 January 2021. N24 was born on 8 February.

The first week of their lives, eaglets are covered with fuzzy down. The proper term is natal down. They can sit up but it is difficult to support their heads and focus. You can see the white dot indicating the egg tooth. This will disappear later. They use the egg tooth to break through the thick shell. This is often called the ‘bobble head’ phase. Their heads are big and they do not yet have the neck strength to keep them upright at all times. Their eyes are adjusting to focus. Sibling rivalry might already have started. As the days progress, the eaglets will get the strength to hold up their head and balance it. They will also be able to focus with their eyes so they do not look like they are using their beak like a dart but with a moving target (often their sibling). While the bobble head stage is very cute, it is often a relief when the eaglets are more stable.

SWFL nest 2021. Sibling rivalry began immediately. E17 is on the right and is only two hours older than the twin, E18. This rivalry persists but has dissipated to being only occasional and directly related to feeding.
The egg tooth is clearly present on the eaglet to the left.

By week two, the eaglets will be observed crawling out of the nest bowl. They are not walking. They are crawling. N24 is using its feet and wings to help it get out of the nest cup and up to the pantry. It is five days old! Food is a great motivator! Samson has the little one ‘working’ for its dinner. This helps to strengthen its wings and legs. In the Captiva Florida Eagle nest, Peace climbed out of the nest bowl towards the food on day 2. The inclines of both nests are different. The parents present the eaglets with challenges to help them develop their strength such as stretching their necks, grabbing and holding food, working their legs and wings. It’s like having your own personal trainer!

N24 crawling out of the nest cup on 13 February 2021, 5 days old

The beak will begin to grow and the little ones should begin shooting the ‘ps’ out of the nest bowl by the end of week one or beginning of week two.

N24 doing a great pose to get that PS clear of the nest. Watch out mom!

The eaglets are more observant of their world. They will have doubled in size from the day they hatched and their eyes and beak continue to develop. You will begin to notice that pin feathers are growing in at their wing tips. They will start to stand keeping their balance with these wing tips.

N24 12 days old. Notice the feathers coming in on the wing tip (left side)

More feathers begin to appear on the shoulders and the back and the wing feathers are getting longer as the days progress. They are starting to wing flap and they will try picking up food.

N24 wing flapping, 12 days old

N24 is twelve days old in the picture above and the one below. In the one below, you can also see the pin feathers right at the tip of the wing starting to come in. N24 is also standing for several seconds, getting its balance, and flapping those wings.

N24, 12 days old. Wing flapping.

During the third and fourth week, a pattern of accelerated feedings and growth begins. Head and chest are still showing signs of some fluffy down but more dark feathers are starting to emerge.

E17, SWFL Nest, Age 31 days

The eaglets are actively preening those feathers to help condition them as well as to help stop what some say is an itching as the feathers grow in. There is more wing flapping and the eaglets stand with confidence and stability. During this time you will see attempts at standing and walking. They begin to make some effort at self feeding. They are eating much more at each feeding often lunging at the parent to take the food out of their beak. Many observers say that their crops appear like they could burst! These big feedings often result in the eaglets sleeping immediately after a feeding. This is a ‘food coma’. The enlarged crops are extra storage spaces where food is held before being ‘dropped’ to the stomach. Sometimes people call this accelerated growth period the ‘clown feet’ era because the feet seem to grow way out of proportion to the rest of their body. They will also cast pellets. Pellets are food that is undigested such as fur and bones. Pellets are compressed into a hard shape and regurgitated. This often involves coughing and sometimes the eaglets appear not to want to eat the day the pellet is cast. This level of peak energy demands appears to begin to wane after about five to six weeks.

E18 has its wings dropped while sitting (eaglet on left). Crop is full. 23 February 2021.

Beginning around week five to eight, the eaglets often sit with their wings drooping (getting heavy). Hopping and flapping wings occurs more often. They are very interested in what is happening outside the nest. By the end of this period, they will begin to have more of their juvenile plumage colouration. They will be able to hold food and tear bits. They will begin to mantle food. Mantling is the covering of food with the wings in order to have the prey item to themselves. They will stand for longer periods of time and are able to walk easily by the end of the period.

From week nine to fledging. The feathers will become more defined over their entire body and they will stand for longer periods of time upright. They can stand easily on one leg. The hopping, jumping, and flapping of wings accelerates. They are self-feeding but the parents will also continue to feed them. They will now spend their nights sleeping upright like their parents with their head tucked under their wing. They can easily perch on the edge or rim of the nest and will be branching, hopping up to a branch and back down into the nest. Branching tends to occur from seven to ten days before fledging, generally.

Juvenile feathers are not all in. E9, 2017.
E9 Branching, 2017.
E9 trying out a thinner branch, 2017.

It is always exciting to see the eaglet hatch and sad when they fledge. Unless there is a transmitter or bands, they fledge and there whereabouts often goes unknown. Once they are wholly independent of their parents, the juveniles need to find their own territory and source of prey. Sadly, fifty percent of all first year eaglets perish while ninety percent of all year two eaglets tend to survive. The average age of maturity for Bald Eagles is five to six years although there is a young sub-adult male who is incubating his first eggs with his mate in Minnesota right now.

Thank you so much for joining me today. Stay safe. Be well.

Thank you to the Eagle streaming cams at NEFL and SWFL as well as the D Pritchett family. The scaps came from their streams.

Day 11 of incubation

It is noon on Daisy’s nest in the Sydney Olympic Park forest. She has started to pant as the sun shines directly on her. Like other birds, panting is a way for Daisy to regulate her temperature; she does not sweat like humans. It is, as summer days go, hot. The weather at Homebush Bay indicates that it is 34.1 degrees C. I wonder if it is actually hotter on the nest?? It is normally understood that heat rises. And, as you can see from the image below, Daisy is in direct sunlight right now. Some parts of Australia are bracing themselves for very hot weather in a few days, up to 39 degrees C.

The hot sun at high noon is shining directly on Daisy.

Many have thought that Daisy would need to take more breaks during the day as the heat builds. However, since it is 12:30 and she remains, I am thinking that she will follow her regular pattern of going off in the afternoon to forage. She has now gathered up more down to cover up the eggs from predators.

At 13:18 Daisy begins to take the down of the nest cup and fold it over inwards. Sometimes she just does this and then will turn and do her cute tail wiggle. Occasionally, she does this when she is rolling her eggs but, most often, it is a sign that she is thinking about leaving to eat. Remember, Daisy does, if all things go serenely, have a pattern of leaving the nest between 1300 and 1400 to forage. Yesterday it was 14:02. And yesterday, she returned at 16:49 but noticed both WBSE on the camera tree and aborted her landing on the nest. So, on average, if voluntarily, it appears that she takes about a two and a half to a three hour break.

In the images below, Daisy begins to tuck the down in around the egg cup. Once the down is folded onto the top of the eggs, she then goes about placing leaves and plant material, and small twigs to further disguise the location. It took her eight minutes to get everything right so that she can leave. She departed at 13:26.

Daisy is busy folding the down that lines the nest cup inward.
Very methodically she continues folding the down in a clockwise direction.
After folding the down, Daisy begins to use her bill to bring in plant material.
It is not always easy to move the leaves and twigs with her bill but Daisy is tenacious.
Once she is satisfied that the eggs are covered as best she can, she leaves to forage to keep up her strength. It is very hot in Hornbush Bay and she needs food and water.
Daisy’s nest is nicely concealed.

All birds have predators and Daisy is particularly vulnerable as she is an outsider to the forest. Her presence and her seven eggs have caught the attention of some, like the Raven and Pied Currawong, that would eat her eggs. Like Daisy’s plumage that serves as camouflage, the manner in which she has concealed her nest is meant to distract any potential threats. She has used the leaves and plant material on top. They blend in perfectly, there is absolutely nothing that would call attention. Daisy is also very discreet and alert in her comings and goings from the nest. Every move is slow and calculated unless she is frightened off by the approaching sea eagles or if she notices their arrival in another tree. Then she leaves quickly!

This is day 11 of Daisy’s brooding or incubation. Even though the eggs were laid on different days, Daisy did not start hard incubation until the last egg was in the nest. Imagine that one minute there are eggs, and within a few minutes the nest will be brimming full of peeping and clacking ducklings. This is precisely what will happen. This is known as synchronized hatching. The number of incubation days to hatching varies but is normally 28-30.

Daisy’s little ducklings – should the nest survive and they make it through the forest to the water – will be covered with fuzzy yellow down. They will have a characteristic dark chocolate brown-black line running from their bill through their eye. There are some white patches on their wings. They will be ever so cute!

Black Pacific Ducklings

Daisy’s ducklings are precocial at hatch. This means that they do not need Daisy to feed them. Daisy’s role will be to lead them to the water where they can forage themselves. Daisy will also help them to learn about predators and she will keep them warm in the evening. In a couple of months their new plumage will be that of an adult Black Pacific Duck, like Daisy.

They are known as ‘dabbling or puddle ducks’. They feed by tipping rather than diving to the bottom of the shallow water. They often forage at the edge of the river and lake like they are doing in the images below. They do not, however, hunt for food on land.

Black Pacific Ducks foraging on the shore. Image courtesy of Wikimedia Commons.
Dabbling along the muddy shoreline. Image courtesy of Wikimedia Commons.
A great image of a Black Pacific Duck foraging in shallow water. Image courtesy of Wikimedia Commons.

It is due to be another hot day in the forest tomorrow. The prediction is that it will be 37 degrees Celsius. This might turn out quite well for Daisy as the White Bellied Sea Eagles could be at Goat Island enjoying the cooler weather near the water. It is 16:42 and Daisy has not returned to her nest. She will be enjoying the cool waters of the canal and the river and, since it is so hot, might decide til near dusk when it is safe for her to return to her nest. The sea eagles are normally roosting then.

An uneventful day is a good day for Daisy the Duck.

Thanks for dropping by to check on the little duck who is occupying the large sea eagle’s nest in Sydney Olympic Park forest. Stay safe everyone. See you tomorrow!

I am grateful for the Sea Eagle cam, Birdlife Australia, and the Discovery centre for the cameras they support. This is where I get my scaps.