I know that this can be tough but if by any chance somebody was able to notice (links to photos of course would be great) Osprey catching, transporting and eating very small fish I would appreciate posting the estimated fish size. Here is an example of the smallest fish I saw caught and transported by an Osprey:
http://www.pbase.com/image/135485930 - estimated total fish length about 15.8 cm, total body length about 12.5 cm.
I think it was a Spotted Sucker (based on fin color and the several longitudinal rows of dark spots) but I could be wrong and will appreciate correction or suggestions what another species could possibly be taken under consideration.
True, it is my curiosity to find out what is a smallest fish Osprey can catch and transport in its talons but there is also another reason. In published literature there is one paper (Van Daele, L. J. and H. A. Van Daele. 1982. Factors affecting the productivity of Ospreys nesting in west-central Idaho. Condor 84:292-299.) that describe studies done on Osprey diet. Fishes were divided in classes by length with one class less than 10 cm (authors used total length). In this class authors recorded 5 fishes (3.3% of total recorded, n=152). Authors used nets to collect opercula under nests and perches and used those to estimate fish sizes. Fish below 10 cm in size is quite ’tiny’ for Osprey to catch it and transport it in its talons - see for comparison my photos of about 15-16 cm fish. According to their estimates Osprey is able to catch and transport a fish half of that length. I just wonder if anybody know about photo showing Osprey with so small fish. I would love to see it. More likely it could be a perch type fish but still it will look quite small inside the claws.
Also I have problem with accuracy when estimating diet using this method (collecting opercula). Here is one paragraph from this paper: “ Operculum shapes were sufficiently different to allow species identification except in the case of salmonids. Thus, mountain whitefish, rainbow trout, coho salmon and kokanee salmon were only identified to the family level. The species composition of opercula found at perching and nesting sites was not significantly different (P > 0.05) from what we observed captured by Ospreys. However, in prey collections from perching sites, yellow perch were significantly more abundant than in collections from below nests( P < 0.05). This suggests that collections must be made from both perching and nesting sites in order to obtain an accurate estimate of the diet of these birds.”
Why I have question about the method? A couple years ago I presented my observations that Osprey often will eat the whole fish (opercula included) and will ‘discard’ sometimes a few parts either accidentally or when having problem to handle them. This is more likely to happen when eating on perch; a branch, post, etc. when Osprey has no chance to retrieve dropped parts. Dining on the nest is different. There are some fishes (e.g. catfish or very large fish) whose some parts are too difficult to eat (to tear off or to swallow). So taking under the consideration that Ospreys will often consume the whole fish a method of collecting fish opercula cannot be very accurate to estimate their diet, especially when fish remains are collected at the nest.
I uploaded a short video showing an example of Osprey (this time a chick fed by a female) having no problem to eat all body parts of a small-medium fish; including opercula and internal organs (other parts of fish that are often listed as being discarded). In fact I choose the case when operculum was dropped and retrieved.
Again, I will appreciate any information about the records of smallest fishes taken by Ospreys.
Thanks in advance
All the best,