At 3½ weeks old both the osprey chicks are doing fantastically well. It hasn't rained on the Dyfi in July yet and that has meant good fishing weather for Monty and in turn plenty of fish for the growing youngsters. (Update: it's starting to rain for the first time at 11:02, July 24th!!)

The growth spurt at this age is incredible. Have a look at the two videos below (choose HD for best resolution). They are taken exactly one week apart when the ospreys were around two weeks old and three weeks old.

Two weeks of age

Three weeks of age

Can you see subtle differences in behaviour between both feeding events, one week apart? Notice a difference in the chicks' food soliciting calls and also Glesni's less delicate approach to choosing fish morsel size at three weeks old. Basically, at three weeks old the chicks can deal with their prey a lot easier meaning less processing time and effort for Glesni.

And here's the reason for this growth spurt. Since the chicks hatched, the amount of fish brought back to the nest has doubled from around 13 per week to 26. Have a look at the graph below to see this sudden increase in fish caught.

And here is the breakdown of the species caught, about the same as the last two years. Half are mullet, a quarter trout, and a fifth flounder.

This exponential growth spurt will continue for another couple of weeks, by which time the chicks will weigh more or less what they'll weigh as adults. Thereafter, it's the flight feathers that continue to grow, particularly tail and wing feathers.

Here's the oldest chick having a rest while he/she puts on several grams of weight each day. That white spot at the end of the beak is the remnants of the egg tooth that the chick used less than four weeks ago to chip out of its egg. In another week, that will be gone.

Ringing and Tracking

Both the Dyfi chicks will be ringed this year when they are five weeks old or just after - around August 5th/6th/7th depending on the weather. We'll put a small metal British Trust for Ornithology ring on their left leg and a plastic 'Darvic' ring on their right leg so that they can be identified in the wild. This is the same way around as England; in Scotland it's the other way around (i.e. Darvic goes on the left leg).

Darvic rings - a Welsh osprey wearing one of these rings is now an experienced breeding male in Scotland.

Most of the countries in Europe have now adopted a particular colour ring for ospreys. Germany has black for example, France is orange, Spain is yellow. In the UK the colour for ospreys is Blue with two characters carved on each ring, replicated three times, reading up from the foot, but from around 2012 onwards some newer blue rings have three characters.

Einion being ringed in 2011 with a UK blue coloured ring

The ringing operation usually takes less than an hour. The osprey parents will be circling overhead calling to their chicks to 'play dead' while we ladder up to the nest, gently take the chicks out and lower them to the ground to be ringed. They will also be measured and weighed.

We will also give them a quick heath check by looking at their overall condition and looking for any fault-bars on the feathers. These are weak points in the feathers, thin yellow lines usually, that represent a time in the chicks' life where food was scarce and it didn't have enough calories to grow at a healthy rate that day. We don't expect to find any with our two this year!  

Osprey chicks at five weeks old can weigh anywhere between 1000g and 2000g. A healthy male should weigh in at between 1300g and 1600g and a healthy female 1500g and upwards, but there can be overlaps so judging the gender of a chick by its weight alone is not advisable. We'll also look at the head size, the beak size, the tarsi (thickness of the legs) and the overall size of the bird. Without DNA testing, it is still a guessing game however. Plenty of ospreys have been labelled the wrong sex as a chick only to return to the UK to breed as the opposite sex!

We will use the blue rings 1R and 2R for this year's birds

We have decided not to satellite track the young ospreys this summer and skip a year. The decision is partially to do with cost and the logistics of fitting the trackers on birds which are a month behind other ospreys in the UK in terms of timing. It is chiefly to do with resources however.

Behind the scenes as it were, we are crazy busy building the Observatory, the boardwalk system to it, and all the interpretation (hence less blogs this year, sorry). Montgomeryshire Wildlife Trust is a small charity with only a handful of staff working long hours to protect and conserve wildlife. We punch above our weight on many levels but the resources, time and effort required to track these ospreys this year and then process the data and make this available on Google Earth and on the website is just a level too far for this year. We could probably do it, but not up to our usual standard. We strive for excellence in everything that we do, and we simply could not maintain that standard this autumn. If something is worth doing, it's worth doing well.

Einion, Leri, and Dulas in the nest in 2011

Shall we name the chicks this year? Yes, why not!

It's not everyone's cup of tea but it doesn't half make it easier to refer to these birds when we talk about them in the visitor centre, the hide, and on blogs and social media. After all, we name our cars, pets, buildings, houses and even our own children. At the end of the day, it makes not one jot of difference to the birds themselves - they haven't a clue we've named them. (Although Alwyn still maintains that, in his excitement of seeing our male bird return on April 6th in 2010, the osprey looked straight at him for 4.7 seconds after Alwyn shouted 'M-O-N-T-Y' directly at him at 150dB from the osprey hide!)

We will name them after we ring them in a couple of weeks and when we have a better idea what sex they are. After saying that though, it does look more likely as each day passes that we have one boy and one girl!

What do you think?