OOooo Fishy, Fishy, Fishy, Fish!

This week I’m going to talk about one of two species of diurnal raptor which occurs on all 6 habitable continents (Antarctica being inhabitable to raptors). The other of course being Falco peregrinus (peregrine falcon) which I’ve covered on my second post, this time it is about a bird of prey commonly known as the osprey or fish eagle/hawk. Ospreys (Pandion haliaetus) is a monotypic species of raptor which feeds almost entirely on fish, both freshwater and salt water species usually between 100-300g (Ferguson-Lees and Christie, 2001). Although their range is large, the breeding range is almost entirely Holarctic and Australasian, and most populations are migratory (Ferguson-Lees and Christie, 2001).

Figure 1. Map of global distribution of Pandion haliaetus. Darker shades indicate areas which breeding occurs, resident or at least regular occurance throughout the year. Light shade indicate regular presence but does not breed. (Ferguson-Lees and Christie, 2001)

Genetically Pandionidae forms a clade with Sagittaridae (secretarybirds), and Accipitridae (hawks, eagles, old world vultures, kites etc.), Pandionidae being closer related to Accipitridae than to Sagittaridae (Nishida et al., 2014). However this being said, the karyotypes of the different families are very different, Nishida et al. (2014) suggests that 2 major episode of chromosome rearrangement occurred within the clade; fission of macrochromosomes occurred frequently in ancestral forms and a high frequency of microchromosomal fusions in the lineage of Pandionidae and Accipitridae.

Pandion haliaetus with prey fish, at Morro Strand State Beach near Azure Street, Morro Bay, CA (Baird, 2006)

Since I live in Australia, let’s have a closer look at the Australasian Ospreys (P.h.cristatus), this subspecies of osprey is distributed from Indonesia down to Tasmania along the coast (Dennis and Clancy, 2014, Ferguson-Lees and Christie, 2001). The main morphological difference between P.h.crisatus and its Northern Hemisphere counterparts is that they are generally 12 – 14% smaller for both sexes (Dennis and Clancy, 2014, Ferguson-Lees and Christie, 2001). The highest population density of P.h.cristatus is in the tropical coastline of Australia, mainly Northern Territory and Western Australia. Incidentally the abundance of osprey lowers where urban development and tourism infrastructures are more extensive (Dennis and Clancy, 2014).

P.h.cristatus feeding on perch at Coral Bay, Western Australia 

(User: Psylexic, 2007)

Interestingly people have had some interesting views on the osprey, like how the fish would surrender itself to the osprey belly up, a helpless prey against the raptor(Cocker and Mabey, 2005). This notion was even used by Shakespeare in one of his final tragedy Coriolanus:

“I think he'll be to Rome As is the osprey to the fish, who takes it By sovereignty of nature.” (Shakespeare, 2010).

On that note, I think that’s enough for today’s post.

BAIRD, M. L. 2006. Osprey with fish. Wikipedia: Mike Baird. 

COCKER, M. & MABEY, R. 2005. Birds britannica, Random House.

DENNIS, T. E. & CLANCY, G. P. 2014. The Status of the Osprey (Pandion haliaetus cristatus) in Australia. Journal of Raptor Research, 48, 408-414.

FERGUSON-LEES, J. & CHRISTIE, D. A. 2001. Raptors of the world, Houghton Mifflin Harcourt.

NISHIDA, C., ISHISHITA, S., YAMADA, K., GRIFFIN, D. K. & MATSUDA, Y. 2014. Dynamic Chromosome Reorganization in the Osprey (Pandion haliaetus, Pandionidae, Falconiformes): Relationship between Chromosome Size and the Chromosomal Distribution of Centromeric Repetitive DNA Sequences. Cytogenetic and Genome Research, 142, 179-189.

SHAKESPEARE, W. 2010. Coriolanus, Cambridge University Press.

USER: PSYLEXIC 2007. Pandion cristatus. Wikipedia.

The Brave and the Bold

Aquila audax translated to the bold eagle, commonly referred to as the wedge-tailed eagle, is the largest bird of prey species in Australia. With a wingspan of up to 2.5m they soar above the Australian outback. Although primarily feeding on rabbits in rabbit affected areas, they also feed on a wide range of prey from hares, goannas, feral cats all the way up to young wallabies and kangaroos (they can carry prey up to at least 5kg) as well as carrion during droughts (Ferguson-Lees and Christie, 2001, Olsen et al., 2014). Wedge tails have been known to exhibit some interesting behaviours, although usually solitary or in pairs they have been known to cooperate in order to hunt down large preys either as a pair or sometimes more; there is a record of 15 eagles hunting a red kangaroo (Macropus rufus) which is the largest species of macropod which can weigh up to 90kg (Ferguson-Lees and Christie, 2001, Richardson, 2012).

Figure.1 Aquila audax in flight over Swifts Creek, Victoria. (user:fir0002, 2007)

There are two subspecies of this Australian endemic raptor, one on the mainland A.a.audax and the Tasmanian subspecies A.a.fleayi which can be differentiated by the whitish buff by the nape of the eagle compared to the tawny rufous of the mainland subspecies (Ferguson-Lees and Christie, 2001). Due to the small range, specific habitat requirements and to a large extent human caused mortality from shooting, poisoning and anthropological disturbances resulting in abandoned nests sites, the Tasmanian subspecies is listed as endangered/critically endangered depending on the source, with only 60-80 breeding pairs by the 1990’s (Ferguson-Lees and Christie, 2001, Bekessy et al., 2009). The Tasmanian subspecies has been separate from the mainland population for about 10,000 years, being the only apex predator left in Tasmania since the extinction of the Thylacine cynocephalus puts them in an extremely important ecological role (Bekessy et al., 2009).

Figure 2. A.audax standing over roadkill in Pilbara,
  Western Australia (User: Djambalawa, 2008).

A.audax which commonly hunts in open areas (A.a.fleayi being an exception) where prey aren’t hiding in dense forests, but surprisingly there have been cases both historically as well as recent that suggests wedge tails to forage and possibly hunt in dense closed rainforests of the Wet Tropics in Far North Queensland (Burnett et al., 1996). These diverse hunters are truly something to behold, I only saw my first ever A.audax last week soaring in the sky, I hope next time you drive around you too will be sure to have a look for that distinctive tail gliding above.

BEKESSY, S. A., WINTLE, B. A., GORDON, A., FOX, J. C., CHISHOLM, R., BROWN, B., REGAN, T., MOONEY, N., READ, S. M. & BURGMAN, M. A. 2009. Modelling human impacts on the Tasmanian wedge-tailed eagle (Aquila audax fleayi). Biological Conservation, 142, 2438-2448.

BURNETT, S., WINTER, J. & RUSSELL, R. 1996. Successful Foraging by the Wedge-tailed Eagle <I>Aquila audax</I> in Tropical Rainforest in North Queensland. Emu, 96, 277-280.

USER:DJAMBALAWA 2008. Wedge-tailed Eagle sitting on roadkill carrion in the Pilbara region of Australia. Wikipedia: Djambalawa.

FERGUSON-LEES, J. & CHRISTIE, D. A. 2001. Raptors of the world, Houghton Mifflin Harcourt.

USER: FIR0002 2007. Wedge-tailed Eagle (Aquila audax) in flight. Wikipedia: fir0002.

OLSEN, J., COOKE, B., TROST, S. & JUDGE, D. 2014. Is wedge-tailed eagle, Aquila audax, survival and breeding success closely linked to the abundance of European rabbits, Oryctolagus cuniculus? Wildlife Research, 41, 95-105.

RICHARDSON, K. 2012. Australia's Amazing Kangaroos: Their Conservation, Unique Biology and Coexistence with Humans, CSIRO publishing.

Can I borrow your burrow?

So here we are again, and this time I’ve decided to pick my first nocturnal bird of prey to write about (YAY!). Who is it you ask? Why it’s the super cute burrowing owl of course. Athene cunicularia more commonly known as the burrowing owl, so named due to their breeding habit of nesting in burrows on the ground created by prairie dogs or ground squirrels depending on their location but they may also nest in synthetic burrows in human populated areas (Martin, 1973, Barclay and Menzel, 2011, Scobie et al., 2014). There is an interesting behaviour which arise from the use of ground squirrel burrows, since rattlesnakes are also known to use ground squirrel burrows A.cunicularia has been known to produce hissing and rattling sound once the burrow has been occupied to simulate defensive sounds of a rattlesnake to ward away squirrels, a classic example of Batesian mimicry (Rowe et al., 1986). This trait as a defensive mechanism however is not common amongst owls, a unique behaviour for a homologous trait (hissing). Furthermore it could also act as a defensive acoustic mimicry to predators such as coyotes and badgers (Rowe et al., 1986).

Due to their large range there are many subspecies of burrowing owls throughout the Americas occupying habitats from open desert grasslands to golf courses and parks in some urban areas (Martin, 1973, Scobie et al., 2014). A.cunicularia is also known to be territorial and may possibly have territories stretching of up to and beyond 166m from nesting sites (Martin, 1973). As with many other animals and plants humans have had an impact on the burrowing owl with habitat encroachment such as roads and infrastructure. With the presence of roads it also means that cars will disturb the adjacent habitat, it has been shown that burrowing owls will avoid roads with traffic travelling 80+ km/hr, as the noise pollution interferes with their predator detection ability as well as communication with mate and young but some man-made structures such as posts do act as valuable perches for the owls (Scobie et al., 2014).

Since I have no pictures today here's a little clip by the Smithsonian on these cute little birds and one very interesting behaviour too.

BARCLAY, J. H. & MENZEL, S. 2011. Apparent Polygynous Nesting by Burrowing Owls. Journal of Raptor Research, 45, 98-100.

MARTIN, D. J. 1973. Selected Aspects of Burrowing Owl Ecology and Behavior. The Condor, 75, 446-456.

ROWE, M. P., COSS, R. G. & OWINGS, D. H. 1986. Rattlesnake Rattles and Burrowing Owl Hisses: A Case of Acoustic Batesian Mimicry. Ethology, 72, 53-71.

SCOBIE, C., BAYNE, E. & WELLICOME, T. 2014. Influence of anthropogenic features and traffic disturbance on burrowing owl diurnal roosting behavior. Endangered Species Research, 24, 73-83.

The Landwalker

Sagittarius serpentarius: taken at Serengeti National Park, Tanzania.
(User:Yoki, 2008)

All birds of prey fly, with no exception. However there is one bird who walks and stomps the grasslands of Africa, the secretarybird (Sagittarius serpentarius) – The snake archer (just a damn cool name). Unlike other birds of prey, S.serpentarius likes to spend most of its time on the ground, preferring to walk rather than run and run rather than fly (Ferguson-Lees and Christie, 2001). Although more terrestrial in nature, S.serpentarius builds their nests in low trees and are monogamous (having a single mate for life) (Ferguson-Lees and Christie, 2001, Hofmeyr et al., 2014).

The secretarybird occupies quite a large range, covering much of sub-Saharan Africa, when they aren’t breeding they tend to be nomadic and are relatively rare to spot. Aside from being nomadic and monogamous, they are also territorial and roosts and builds nests on trees in their territory (Kemp, 1995, Hofmeyr et al., 2014). S.serpentarius shows some interesting behaviours, in flight they they may perform dives at each other, showing their claws at each other; sky dances, which is characteristic of accipitriforme eagles and hawks. Meanwhile, on the ground they chase each other around with wings raised much like cranes and storks (Ferguson-Lees and Christie, 2001).

The last two points should give you a hint to where I’m going with this, yes phylogeny!!! Being part of a monotypic family and genus: Sagittariidae and Sagittarius (that is, there’s only one genus in the family and only one species in the genus), they are considered quite unique. But just how unique are they in terms of phylogeny? Well it turns out there’s still a lot of debate regarding where secretarybirds lie in terms of phylogeny, although it is accepted with genetic testing that they are closer to eagles and hawks (Accipitridae) and ospreys (Pandioniae) than to falcons and storks and cranes, putting them under the order of Accipitriformes (Mahmood et al., 2014).

Fig. 1 Phylogram of families retrieved by matching genes, species marked with star used genome which are reported in the study which this is taken from. Values for bootstrap and pp values are shown at the nodes, * equaling to 100% bootstrap and 1.0 pp value, - equaling less than 60% bootstrap and lower than 0.9 pp value. Nodes where bootstrap and pp are both less than 60% are not shown (Mahmood et al., 2014).

Sagittarius serpentarius flying overhead at
 Tsavo East National Park, Kenya.
(User: putneymark, 2007)

S.serpertarius are listed as vulnerable and have seen a decline in population in recent years, owing to a number of threats including habitat encroachment, afforestation, disturbance of breeding, grazing of livestock removing habitat and being captured or killed by humans (Birdlife International, 2013, Ferguson-Lees and Christie, 2001, Hofmeyr et al., 2014). If we are to keep this archer of snakes around we must plan our developments and stop the habitat degradation and encroachment or it looks like their population will continue to decline.

BIRDLIFE INTERNATIONAL 2013. Sagittarius serpentarius. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 05 April 2015.

FERGUSON-LEES, J. & CHRISTIE, D. A. 2001. Raptors of the world, Houghton Mifflin Harcourt.

HOFMEYR, S. D., SYMES, C. T. & UNDERHILL, L. G. 2014. Secretarybird Sagittarius serpentarius Population Trends and Ecology: Insights from South African Citizen Science Data. PLoS One, 9.

KEMP, A. C. 1995. ASPECTS OF THE BREEDING BIOLOGY AND BEHAVIOUR OF THE SECRETARYBIRD SAGITTARIUS SERPENTARIUS NEAR PRETORIA, SOUTH AFRICA. Ostrich, 66, 61-68.

MAHMOOD, M. T., MCLENACHAN, P. A., GIBB, G. C. & PENNY, D. 2014. Phylogenetic position of avian nocturnal and diurnal raptors. Genome biology and evolution, 6, 326-332.

USER: PUTNEYMARK 2007. secretary bird Tsavo East feb 2007. Available: http://en.wikipedia.org/wiki/Secretarybird#/media/File:Sagittarius_serpentarius_-Tsavo_East_National_Park,_Kenya_-flying-8.jpg; Retrieved 05/04/2015

USER: YOKI 2008. Secretary Bird (Sagittarius serpentarius). Available: http://en.wikipedia.org/wiki/Secretarybird#/media/File:Sagittarius_serpentarius_Sekret%C3%A4r.JPG; Retrieved 05/04/2015