Video Archive - April/May

They're Back!

The ospreys have returned from their winter vacation. The first bird, probably the male,¹ was first seen on April 20th. Usually arriving a few days later² the female was seen the next day.

April 20 April 20

 April 21 April 21

How The Osprey Got Their Pole

Before the era of telephone and electrical poles, osprey primarily used trees as their nesting platforms.³ Described as "gigantic mushrooms" they were often decades old, made of sticks, sod, and a treasure trove of human things, like toy boats, broken oars and rain slickers.⁴ Now ospreys prefer more stable structures that don’t sway in the breeze or bend and crack beneath the strain of 20 years of accumulated nesting materials¹. And if that structure is specifically designed and placed to meet the ospreys needs, so much the better.

The story of this osprey’s pole begins 14 years ago with a man named Brian Keating, the current head of the Calgary Zoo’s Conservation Outreach Program. Seeing osprey around the zoo, Brian decided to provide them with their custom made pole. After painstaking research and a couple of phone calls to wildlife biologists, he chose the best site and erected the first pole. This pole was 17 feet higher and was replaced because only three cherry picker rigs were able to reach that high. Two weeks after the original platform was in place the ospreys were nesting.⁵

Unwanted Visitors

Ospreys are quite willing to share their nest with other birds, but only if there is enough room for everyone . While this nest may seem large, it does not provide any additional space for interspecies roommates. Before our ospreys returned from migration they had some unwanted visitors.

 Geese oops! Geese oops!

If the geese had started to nest on the platform the ospreys would have looked for a different site, or would not have nested at all this year¹. Luckily the large branches left behind proved too tricky for webbed feet to handle.

The Construction Process

Nesting material can be brought to the nest by both birds, but typically the male brings most of the materials leaving the female to arrange them to her liking.¹

 Moving stick Moving stick

While sticks and sod make up most of the nest, other more human items, are often found in the midst of construction.³

 Cloth delivery Cloth delivery

The ospreys will often look for plastic to line their nest with materials that will prevent the eggs from falling through cracks.¹ Luckily the Calgary Zoo is renovating and was able to provide some nesting materials.

 Caution tape delivery Caution tape delivery

The birds carefully intertwined the tape between the branches.

While large, the nest sometimes seems too small. Watch as the male osprey delivers a large stick and the female rearranges it.

 Large stick delivery Large stick delivery

Nest Building - A Picture Timeline

See how the nest grows. Starting from scratch ospreys will take from 10 to 20 days to build their nest.

View Picture Timeline

Mating Rituals

The main goal of any species is to pass on its genetic material. From slime molds to humans, the methods may be different but the results are the same, the next generation! Our ospreys are no different.

 Copulation Copulation

While brief, each pair will copulate an average of 160 times per clutch¹. The success of these monogamous birds relies on more than just the number of times that they mate. They also have mating rituals like courtship display and feeding.

 Fish delivery Fish delivery

Courtship feeding is when the males feed the females exclusively prior to egg laying. This is often a factor that determines clutch size in many bird species². In osprey, while courtship feeding is a factor, the longer that the pair has been together and the age of the birds is more important³. More experienced pairs breed earlier, because they are not looking for a mate, lay larger eggs and clutches, and are better at finding food, because they are experienced hunters³.

It is hard to say whether or not this is the original pair from 14 years ago. I like to think that they could be. We know that osprey do come back to previous nest sites and that more experienced pairs will lay their eggs earlier¹. Our birds laid their first egg 20 days after the female arrived, which is just within the normal 10-20+ day nest building period1.  Finally, the oldest male osprey in the wild lived for 25 years⁴ and the oldest female for 23 years⁵. These could very well be the birds that the pole was built for all those years ago.

The pay off!

Our first egg was laid on May 11th

The second egg was laid on May 15th

The final egg was laid on May 17th.  Most osprey clutches are three eggs.

Sharing the load.

Both male and female osprey share incubation.¹

 Switch male Switch male

The male has switched with the female after bringing her a fish.  He will incubate for 30% of the total incubation time.¹

 Switch female Switch female

After her snack the female returns to take over the bulk of the incubation, which will last for around 37 days.¹

Keeping it clean!

While the nest is made up of many mysterious things, including leftover fish (see previous entry).  Ospreys are not interested in using it as a toilet.  They, like most birds, have perfected the art of projectile pooping!¹

 Keeping the nest clean Keeping the nest clean