I know that some of you have watched birds fall out of nests including Silo Chick at Patuxent River Park last summer. Remember that feeling when you saw that little osplet fall into the water, heard the splash, and saw the others looking down? Felt helpless? Of course. Thankfully that story ended well. I have no idea how many called but the osprey was located and literally tossed back into the nest. It was an enormous relief. Others are not so lucky.
I posted a new owl box streaming cam in Joburg, South Africa just the other day. An orphaned Spotted Eagle owl was put in the box with two other owlets. The mother accepted it! Fantastic. The adopted owl is 5 days older than the other two and it got curious about the outside world today and fell out of the nest box!
What no one knew, at the time, was that the owl landed on a huge platform under the box. If it doesn’t get back into the box on its own, it will be placed back inside the box. Relief.
Yarruga was starving this morning. There were two prey deliveries at the scrape box and there was not a scrap left of either meal.
Yarruga was so excited when the second meal appeared that she could not stand still to eat. She literally ran around the scrape box as in the images below.
Xavier was certainly glad when that feeding was over! There is not a drop left for either of the adults. Yarruga was soooooo hungry after having only 2 feedings yesterday. She does love her food! And she is certainly growing. Look how big she is next to Xavier!
In fact, Yarruga should have had a nice tasty little duckling yesterday but Diamond saw it and quickly took it from Zavier and flew out of the scrape! One has to imagine that this is quite the delicacy (as opposed to the dreaded Starling!). After her injury, I am actually glad that she got it.
Port Lincoln did a nice close up of the juvenile feathering of the three osplets this morning. Just look at the variations in the depth of the white juvenile feather banding. Little bob is in the middle.
As the dominant bird, Little Bob often gets the first bite. She is full and letting the other two have their turns as she looks out to the water in the image below. Of course, I am saying ‘she’ because of her thick legs. Wait til Monday when the banders declare she is a he. How funny! Whatever gender, that bird is gorgeous and I will continue to celebrate the times that she put Big Bob in his place.
There she is below.
Victor Hurley, the main researcher for the Peregrine Falcons in Victoria has been posting information on the 367 Collins Street FB Page. The last posting was on ‘Dispersal’ because, as we know, the falcons will be fledging shortly. I imagine that there are many things in this column that would be of interest to many of you. This is what he wrote:
First Flight Normally, this is not such a serious undertaking as that from an inner city high rise ledge. Normally pre-fledgling Peregrine Falcons will scramble around across their natal cliff for quite some time before taking their first flight. Mostly this is successful and they land high on another ledge or small perch. In a city location they will land on the roof top of another building nearby. If the winds are tricky then things can go south pretty quickly. Once they have mastered their first flight then they will spend increasing time “on the wing” and following and learning from the parents how to hunt. As soon as each youngster achieves their first kill the adults (parents) will stop providing any more food and that youngster is on their own to find food. Once all young are successfully hunting then depending upon the experience and ruthlessness of the adults they will all be chased with serious determination out of the territory altogether. In some cases this may occur in December or even early the nest year. Either way the young tend not to return again to the nest ledge that we have been observing. Maybe occasionally, but then only briefly.
Plumage differencesLeading up to this first flight the adults restrict the level of food resources they bring to the nest. This explains the weight loss of the nestlings. The wings of the nestlings are still growing but they are also losing weight. This makes them lighter with larger wings which provides for a “lower wing loading” which makes their first flight easier. Neat, huh! The other point I thought I would raise here is that of the plumage differences. Peregrine Falcons as with most raptors and many other bird species have a juvenile plumage phase and an adult plumage phase. The juveniles are in essence a brownish colour with vertical splotchy stripes over a “dark milk tea” fawn base colour on the front and dark brown wing, back and head. Whereas the adults have a near black hood for the head, slatey grey wings and back with a soft cream bib and base colour overlayed with fine dark grey-black horizontal stripes. The tail and main wing flight feathers are also longer in the juveniles and they moult shorter feathers with each year as they get older.
Natal dispersal This is the ultimate question. Where and how far do Peregrines disperse to find a place of their own in which to breed. Natal dispersal is the distance (and direction for those interested) in how far fledgling Peregrine Falcons ultimately move to find and establish (read take over for the most part) their own breeding site. Amongst Peregrine Falcons in Victoria, as with most bird species the world over, the females disperse further from their fledging site to breeding site then do males. Based on observing 127 breeding adults with leg bands (placed on them as nestlings) the females dispersed on average 64km (range 6-280km) and males average 25km (rang 1.6-90km). This differing dispersal distance minimises the likelihood of siblings interbreeding. The average age at first breeding is as follows: females 2.6 years (average) and for males 3.3 years (average). Another way of presenting this same data includes presenting the direction as well as the distance males and females disperse. No bias in dispersal direction was recorded.Victoria is a relatively flat area of the planet, its highest point above sea level is Mt Bogong (1,979m) and~80% of Victoria is <200m ASL. So for a predatory species like the Peregrine Falcon that doesn’t migrate annually due to milder winters and having the highest wing loading of any Peregrine sub-species globally, in a state (Victoria) with limited high altitude cliff faces with an abundance of low lying wetlands and associated birdlife and a very diverse range of parrot species what is a cliff nesting raptor to do? A look at all (256) of the Peregrine Falcon nests ever described in Victoria provides the answer to this question. The Peregrine Falcon in Victoria has overcome these obstacles by adopting a range of novel nesting situations (by nesting in stick nests of other birds, tree hollows and of course buildings (a growing trend globally). So this leads to another interesting question. Do those birds raised in one type of nest only adopt others of the same “nest type”? or will they readily disperse to a different type? That is to say, do they become behaviourally “imprinted” on the nest type they are raised on? Again thanks to the long term banding of nestlings and resighting of adults (with telescopes) by volunteers with the Victorian Peregrine Project the natal dispersal patterns of 127 Peregrine Falcons have been identified so far showing that 30.2% have adopted a different (novel) nest type from the one they were hatched and raised in. Between the sexes dispersal patterns are similar with 26% of females and 23% of males adopting different or “novel” nests in which to breed. Combined 30.2% of Peregrines undertake novel natal dispersals to find a place to breed. So the myth of nest type imprinting has been pretty thoroughly exploded with these bird banding results.Further to this, slightly counter-intuitively, novel dispersal events (dispersing from one nest ‘type’ to another) were less dispersive with no sex bias. That is those individuals who adopted a ‘novel’ nest type did so by dispersing a shorter distance on average than those undertaking a typical natal dispersal. Presumably they are doing this in order to exploit a familiar (geographically closer) food/prey resource by adopting a novel nest type in order to remain close by to that prey resource.So back in 1991 when Peregrine Falcons were first identified breeding at 367 Collins Street, Melbourne it was one of only two or three nest sites on built structures that were known. Since then over 20 new sites have been discovered and the number continues to grow. Nest site selection is driven by its proximity to food resources as well as the security (from predators and human disturbance) and how protected the nest is from rainfall and water runoff.Surviving the first two years…The third question (although not chronologically) is what is the survivorship of young Peregrine Falcons in their first two years prior to breeding. Generally, it is accepted that there is a ~a 66% die-off of Peregrine Falcons within their first year. Given the youngest breeding is at two years post hatching I have trawled the VPP database again to investigate causes of mortality of ~240 banded Peregrine Falcons in their first two years post banding. Most banding occurred at or around 24 days post hatching. When considering the various incidents there was no sex bias. That is neither sex is more prone to any cause of death compared to the other. Rock falls, cliff collapses or storms bringing down trees or stick nests have been a surprisingly regular threat to young of this species. The constant and ever present shooting of Peregrine Falcons continues to this day. The first ever band recovery of a Peregrine Falcon in Australia was in 1958 in Victoria. Disease of course is Trichomoniasis and predators varies from Red Foxes, Brown Falcons and even Peregrine Falcons in limited circumstances. Secondary poisoning has generally been a result of pigeon control campaigns.”
This information would, in general, apply to all falcon populations. And if you read all that – it is a ‘Double Whew’ for today. I have been reminded that Victoria Hurley is doing a Q & A tomorrow. I cannot find the link to it. If I do I will send it out later.
Thank you for joining me. Everyone has been fed at least once if not twice already. Diamond is looking much better. No news on WBSE 27 yet and nothing on Grinnell. Take care!
Thank you to the following for their streaming cams where I took my screen captures: Port Lincoln Osprey Project and Charles Sturt University Falcon Cam and Cilla Kinross.