This paper was published in 2008. It’s dedicated to relationships between migrating Short-toed Eagles and local Yellow-legged Gulls in the region of Gibraltar /map/.
• Mosquera M., 2008 – Mobbing of migrant Short-toed Eagles Circaetus gallicus by Yellow-legged Gulls Larus michahellis during their northbound passage over Gibraltar // Gibraltar Bird Report, 7: 51-54. – 
(En).
The following paper was already mentioned on HoverOverUs. Now the PDF of it is available on the Seaturtle.org website:
• Pavón D., Limiñana R., Urios V., Izquierdo A., Yáñez B., Ferrer M. & de la Vega A., 2010 – Autumn migration of juvenile Short-toed Eagles Circaetus gallicus from southeastern Spain // Ardea, 98 (1). P. 113–117. – (En) /map/.
Results of SEO/BirdLife monitoring programme for 2009-2010 is available on the Sociedad Española de Ornitología website – (Es). Census of Short-toed Eagle population in Spain brought new and unexpected data. About 10380 (!) real territories of Short-toed Eagles (pages 28 and 32) were counted. The numbers are much higher than they had been known before.
One more work from Spain. This M. Sc. Thesis by Aidin Niamir is published on the GEM MSc website (the Academic Output section):
• Aidin Niamir, March 2009 – Distribution modelling of the Short-toed Eagle in relation to potential food availability – M.Sc.Thesis: 75 p. – (En).
This paper is available now on a section of Publications in scientific journals of the University of Granada website:
• Gil-Sánchez J.M., Pleguezuelos J.M., 2001 – Prey and prey-size selection by the Short-toed eagle (Circaetus gallicus) during the breeding season in Granada (south-eastern Spain) // Journal of Zoology (Lond.), 255 (1): 131-137. – (En) /map/.
…and an abstract of next one is placed on a website of Ardea – the official scientific journal of the Netherlands Ornithologists’ Union:
• Pavón D., Limiñana R., Urios V., Izquierdo A., Yáñez B., Ferrer M. & de la Vega A., 2010 – Autumn migration of juvenile Short-toed Eagles Circaetus gallicus from southeastern Spain // Ardea, 98 (1). P. 113–117. (En) /map/.
Heartfelt thanks to Ciro Patricio Romero for publishing his M.Sc.Thesis on our site! Relations between Short-toed Eagle population and snakes populations in Spain are examined in the thesis:
• Ciro Patricio Romero, March 2010 – Examining the possible effect of forest area, abundance of snakes and snake species richness on the abundance of Short-toed Eagle, in Spain – M.Sc.Thesis: 110 p. – (En) {rough translation}.
This is one more article from the Ardeola website:
• IRIBARRER, J.J. and RODRÍGUEZ-ARBELOA, A.., 1973 – Observaciones en un nido del Águila Culebrera (Circaetus gallicus), Navarra 1972 [Observations on a nest of Short-toed Eagle, Navarra 1972] // Ardeola 19(1), 101-106. – (Es) /map/.
The text was published in 1973 including some black-and-white images. The placed PDF file is not of the best quality, but it’s fairly readable.