The Continuing Saga of Dad and the Duck or ‘As the Nest Turns’

Just to bring those of you up to speed in case you haven’t read my earlier blog. In early December, a pair of Pacific Black Ducks investigated the nest of a pair of White-Bellied Sea Eagles (WBSE) in an old Ironwood Tree in the forest of the Sydney Olympic Park in Sydney, Australia. On 14 December, a nest cup was excavated in the centre of the sea eagle nest by the ducks. (Note: This is off-season for the sea eagles.). Six days later, ‘Dad’, the male partner of ‘Lady’, to whom the nest belongs, came to the nest for one of his periodic territory checks. The female aptly named ‘Daisy’ by Phyllis Robbins of the WBSE chat group laid her first egg in the nest cup on 5 January 2021.

Female Black Pacific Duck

On the morning of 11 January, Daisy arrives at the nest just after dawn. Before she could lay her egg, vocalizations from other birds in the forest alert her that the sea eagle is about. Indeed, Daisy might have been listening for the male sea eagle because he had come to the nest the previous day. That day she quickly covered the eggs and flew off the nest but stayed in proximity. Dad stayed for about half an hour before leaving and within a few minutes, Daisy returned to lay her sixth egg without interruption. This morning, however, Daisy had not laid her egg when the large sea bird appeared. She stood on the rim of the nest and quacked as Dad flew to the camera tree. She left so abruptly that she did not have time to cover her eggs but, it seems that Dad did not notice her physical presence on the nest or her quacking.

Dad surveyed his territory remaining on the tree that supports the camera for the live stream for about an hour. He might have thought that the bird laying the eggs would return without noticing him and he would find out who this mysterious bird is.

White-Bellied Sea Eagle Male known as ‘Dad’ scanning his territory for intruders.

After about an hour and a half, Dad flew to the nest tree to see first hand what was happening. He had noticed the eggs the previous day by rummaging around in the leaves. He even tried to pick one up with his bill but to no avail.

Three of the six Black Pacific Duck Eggs

Today the eggs were clearly visible. Look carefully. Daisy has started removing down from her breast to line the nest. This physiological process is called zugunruhe.

Under normal circumstances, Daisy would arrive at dawn to lay her egg. She would do this every day until she finished laying all of the eggs for her clutch. This can vary between 8-13 eggs. After laying her egg, Daisy often remains on the nest for a period of about an hour before departing for the river to forage for the rest of the day. Once all of the eggs are laid, Daisy will begin full incubation, being relieved periodically by her mate. After twenty-eight days, the ducklings will hatch. Then, the following day (after 24 hours), they will take a giant leap of faith and jump off the rim of the nest, a distance of approximately fourteen metres, to the forest floor. Here they will follow their mother to the Parramatta River where they will immediately begin foraging for themselves.

Dad inspecting the Black Pacific Duck’s eggs

Today, Dad began to curiously inspect the nest with the eggs. For what seemed like an eternity, he would look at the eggs and then look around the immediate environment of the tree. It was actually like he was confused. At one point he tried to pick up one of the eggs but he couldn’t do it. It isn’t that they are heavy; the shape is just awkward for him to handle with his beak. He did not try to move the eggs with his giant talons nor did he attempt to break them. He did toss some of the down around. At one point, it even looked like he might start brooding the eggs. It was a very strange exchange because Dad’s hormones are not thinking about breeding or brooding. He is in the midst of moulting.

Dad trying to move one of the eggs

The entire morning was very suspenseful. Currawongs and Sulphur-Crested Cockatoos were screeching in the background and at one point, it was thought that Daisy even did a fly by.

And then the oddest thing happened. Very delicately, Dad covered up the eggs at 9:01 am.

Dad covered up the duck eggs so that no one could see them

If that wasn’t peculiar enough, Dad went up to one of the ‘parent branches’ on the nest tree and stood vigil. More than once, Dad flapped his wings to keep the Currawongs away! Take altogether, these three actions scream out that his intuition is to protect the eggs.

Dad standing guard over the nest

Dad stayed for more than an hour before departing. At the time of this writing, he has returned once again to the nest tree where he is keeping watch over his territory.

Stay tuned!

Why are female Red-tail Hawks almost always 30% larger than the males?

It is called Reverse Sex-size diamorphism. There are several theories as to why this happens with Red-Tail Hawks.

The first is that the females had to be larger to protect themselves from the feisty males.

The second is that the females selected smaller males to be their mates because the size difference allows each of them to hunt different prey and reduce any competition for food between the pair. Raptors that hunt birds are generally smaller and faster with the female specializing on larger prey. At the beginning of the nesting season, the female becomes an active hunter and again when the nestlings are larger. Generally the adults tend to partition the prey resources in their territory.

Another theory is that the females need to be larger because they must accumulate reserves in order to produce eggs. When they are incubating eggs and brooding young, they rely on the male to feed the family. Red-tail hawks are usually born in April when the prey are sluggish and just coming out of hibernation. Small males can make quick turns. In the case of the Red-tails on the Cornell Campus, Arthur W, the male, is known as the ‘stealth bullet.’ He is quick, fast, focused, and quiet when he hunts. Big Red’s former mate, Ezra, was like Arthur W a great hunter but he was also about 30% smaller than Big Red as is Arthur.

Ezra has his wings spread and his legs tucked tight. If you look closely you will see that he is delivering two items to Big Red. The first is a snake and the second is a flower!
It is very difficult to get Big Red and Arthur to stand up straight at the same time. They certainly do not listen to requests from humans!This is the closest I have come to finding an image that might be able to show you the difference in their size. Big Red is on the left and has her head leaning back preening and she is a little more slumped than Arthur who is on the right.

In terms of the nestlings, the only way to positively known the gender of the bird is through either a DNA sample or you see them laying an egg when they are older. Everyone likes to guess the sex of the chicks growing in the nest cup. Using reverse sex-size diamorphism, we speculation whois a female by their overall size as they grow in the nest and the size of their feet. But again, no one can be absolutely sure. In the past one of the small nestlings was always believed to be a male. This particular bird injured its wing and, as a result, had to be taken to a vet. The bird’s DNA was tested and, to the surprise of many, it was determined to be a female. So not every small Red-tail Hawk is a male!

In terms of the relative size of each J, J1 is the largest of the three. Early in its development, everyone noticed the large size of its feet. Now as a juvenile, J1 remains the largest of the three siblings. But there is something else about J1 that I personally find fascinating. J1 is very much interested in nest maintenance. She can be seen, even today, mimicking Big Red in attempts to vent the nest bowl. She rearranges the nest twigs and on the second day after she fledged, she brought a branch to the top of the Rice patio. There seems to be 100% agreement that J1 is going to be a good mama like her mother, Big Red.

J3 in the front and J1 behind watching J2 fledge. Look at the difference in the size of their legs as a starting point.

J2 on the other hand is also a large bird, not as large as J1 but larger than J3. J2 was actually the first egg to be laid but the second to hatch and is, therefore, actually the oldest. His fledge was more like a fludge when he climbed up on the light box and then slipped but his flight was still remarkable. J2 has continued to be a very, very strong flyer already interested in hunting. The shape of “his” head – you will notice that I continue to use the term “his” – is also different than that of J1. He has an intense focus and besides bugs and insects he has already been interested in small birds in the territory. To my knowledge he has not caught one. He is also very aggressive. A few of us believe he is truly a male and will be a great hunter like his dad, Arthur W.

J3 eating his first prey drop after fledging.

J3 is the problem child that everyone loves. . J3 was born four days after the other two and it was also the last egg to be laid. Taken together, J3 is actually a week younger than its siblings. That is a lot in the life of a Red-Tail Hawk chick. It may also account for the fact that Arthur W brings food to the nest tower in an apparent effort to feed J3 away from the two larger siblings. Let me try to explain what has been happening. Normally the juveniles are spread out being individuals. This trio is quite different according to the people who have monitored all of the broods on camera (since 2012). It is because they tend to congregate together. To hang out. If one is on the Rice patio, all three might be there.

All three on what is called the Rice patio. Arthur W often makes food drops here but it is also a safe and flat site where they can sleep in the sun or practice their skills.

They might all be on one of the towers including the nest tower. Still, on occasion, they go their separate ways.

J1 in one of the oak trees near the Fernow Building looking at a squirrel.

A prey drop is just that – one of the parents dropping lunch. The juveniles will, unless they have recently eaten, fight for the food with the most aggressive mantling the prey. Unless the prey item is too large for the chick to eat all at once, sharing doesn’t seem to happen. So, because of J3s size and a seemingly lack of aggressiveness in comparison to J2, J3 is somewhat at a disadvantage. This is the reason that I believe Arthur W still supplies food on the nest to the little guy.

Arthur has been dropping lunch off to J3 for several days now. This was around 3pm. He seems to be looking for J3 who arrives almost immediately.
J3 mantling the prey that Arthur W dropped on the nest. Remember mantling is a way of protecting the food item so that no one else can steal it.
J3 finishing up his afternoon snack.

For now, the gender of the three juveniles is sheer speculation. There are no banding practices and no GPS monitors on the Js. In other words, no identification. It is only when one of the juveniles might find its way to the vet and be both recognized and tested that the sex would be determined.

Tomorrow we are going to talk about the importance of preening.