Fish-eating birds in Western Port: long-term trends Peter Dann, - PowerPoint PPT Presentation

Fish-eating birds in Western Port: long-term trends Peter Dann, Richard Loyn, Peter Menkhorst, Canran Liu, Birgita Hansen & Moragh Mackay

The most important science gaps… Understanding the Western Port Environment Number 12. Examine the trends in A summary of current knowledge and priorities for future research abundance of fish-eating birds in Western Port. Hansen, B., Menkhorst, P. and Loyn, R. (2011) Western Port Welcomes Waterbirds: Waterbird usage of Western Port. Arthur Rylah Institute for Environmental Research Technical Report Series. No.222. Department of Sustainability and Environment, Heidelberg, Victoria.

Hansen et al (2011) 17/37 species have declined in Western Port since 1974 • Shorebirds - mudflat reclamation in the Yellow Sea? • Waterbirds – 10 years of drought? • Fish-eating birds – mostly residents, local causes? (Dennett & Loyn 2009)

Approach Our approach involved two key steps: 1. An analysis of the trends in abundance for fish-eating birds over the past 25 years (1987-2012) for Western Port and Corner Inlet. 2. An analysis of the declines in relation to the foraging guilds, diets and sizes of the birds, and the timing of any observed change.

Locations of two study areas Essential differences in character are coarser sediments, dominance of Posidonia (seagrass), less developed catchment, reduced freshwater inputs & reduced shoreline in Corner Inlet

Survey methods – Western Port Hansen et al. 2011

Survey methods – West Corner Inlet

Fish-eating birds Surface seizers • Australian Pelican 14 species (13 spp. ate >40% fish in their diets) Underwater pursuit Great Cormorant • 9 species breed in Western Port, other 5 species Pied Cormorant recorded breeding in Victoria Little Pied Cormorant Little Black Cormorant • Fall into 5 feeding guilds Black-faced Cormorant Pursuit divers Crested Tern Caspian Tern Fairy/Little Terns Gull-billed Tern Visual jabbing Eastern Great Egret Little Egret White-faced Heron Filterers Royal Spoonbill

Fish-eating birds (14 species) Total fish-eating birds in summer (Western Port) 1200 NUMBER OF FISH-EATING BIRDS 1000 800 TOTAL (Western Port) R² = 0.2617 600 400 200 1985 1990 1995 2000 2005 2010 2015

Fish-eating birds (14 species) Total fish-eating birds in summer (Corner Inlet) NUMBER OF FISH-EATING BIRDS 2000 1800 1600 1400 1200 1000 800 Total (Corner Inlet) 600 Linear (Total (Corner 400 Inlet) ) 200 0 R² = 0.62 1985 1995 2005 2015

Fish-eating birds in summer (Western Port & Corner Inlet) . 2000 1800 NUMBER OF FISH-EATING BIRDS 1600 1400 1200 1000 800 TOTAL (Western Port) 600 R² = 0.2617 400 Total (Corner Inlet) 200 R² = 0.62 0 1985 1995 2005 2015

Fish-eating birds in winter (Western Port & Corner Inlet) 2500 Total (Corner Inlet) Winter Total (Western Port) Winter 2000 NUMBER OF FISH-EATING BIRDS Linear (Total (Western Port) R² = 0.305 Winter) 1500 1000 500 0 1985 1995 2005 2015

Trends & guild type Pelican- no significant trend Cormorants – no significant trend Herons & egrets – no significant trend Terns – significant decline in numbers Royal Spoonbills - significant decline in numbers

Trends in tern numbers in Western Port (summer) 300 CASPIAN TERN CRESTED TERN TRENDLINE R² = 0.29 250 FAIRY/LITTLE TERN CRESTED TERN 200 Linear (FAIRY/LITTLE TERN) NUMBER OF TERNS Linear (CRESTED TERN) 150 100 50 0 FAIRY/LITTLE TERN TRENDLINE 1985 1990 1995 2000 2005 2010 2015 R² = 0.18

Crested Terns in summer and annual commercial catch

Numbers of breeding Royal Spoonbills in Western Port & Corner Inlet 250 200 WESTERN PORT R² = 0.36 CORNER INLET 150 Linear (WESTERN PORT) Linear (CORNER INLET) R² = 0.24 100 50 0 1985 1990 1995 2000 2005 2010 2015

What do Crested & Fairy/Little Terns eat? Main fish in diet % fish in diet Crested Tern Anchovy Engraulis australis 93% frequency of Chiaradia et al. (2002) Jack Mackerel Trachurus declivis occurrence brought to Barracouta Thyrsites atun chicks at Nobbies, Phillip Island Fairy/Little Tern Pilchard Sardinops sagax Mostly fish Taylor & Roe (2004) Anchovy Blue sprat Spratelloides robustus Royal Spoonbill Bridled Goby Arenigobius bifrenatus 23% wet weight of prey Lowe (1982) in Western Port

Summary: Crested Terns Pursuit diving guild has declined significantly, mainly Crested Terns and Fairy/Little Terns Crested Terns have decreased in number inside Western Port but breeding numbers have increased greatly at the western entrance. Crested Terns numbers have increased in Corner Inlet in summer . Conclusion: Crested Terns use of Western Port for feeding has declined. while the local breeding populations of Crested Terns has increased. Management actions required: Develop abundance measures for monitoring key fish species in Western • Port

Summary: Fairy/Little Terns Little/Fairy Terns numbers vary widely and appear to have decreased both in number feeding in Western Port & Corner Inlet and probably breeding locally. Conclusion: Fairy/Little Terns’ use of Western Port & Corner Inlet for feeding have declined. Management actions required: The decline of this species appears more widespread and a review of • current trends and management across Victoria is required. Develop abundance measures for monitoring key fish species in Western • Port

Summary: Royal Spoonbills Royal Spoonbills have declined significantly in Western Port in summer and have increased in Corner Inlet in summer . Likely that they haven’t bred very successfully in Western Port over the last decade due to drought affecting breeding sites. Conclusion: Numbers in Western Port have declined for reasons that haven’t operated in Corner Inlet. Management actions required: Continue to monitor numbers at high-tide • roosts Monitor numbers and productivity of • breeding colonies in Western Port

Acknowledgements Rhys Coleman of Melbourne Water for commissioning us to do this work, with funding from the Port Phillip and Westernport Catchment Management Authority through the Victorian Government’s Natural Resources Investment Program (NRIP). BOCA (now Birdlife Australia ) Western Port count volunteer s since 1974. DSE - Fisheries & Wildlife & Parks Victoria & many volunteers who have helped in Corner Inlet since 1981. Rhys Coleman & Will Steele for comments on this analysis. Jeff Lacey for use of his Fairy Tern counts. Phillip Island Nature Parks and Victorian Wader Study Group for data on breeding Crested Tern numbers at the Nobbies.