SLIDE 1
Fish-eating birds in Western Port: long-term trends
Peter Dann, Richard Loyn, Peter Menkhorst, Canran Liu, Birgita Hansen & Moragh Mackay
SLIDE 2 The most important science gaps…
Number 12. Examine the trends in 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
- f Sustainability and Environment,
Heidelberg, Victoria.
Understanding the
Western Port Environment
A summary of current knowledge and priorities for future research
SLIDE 3 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)
SLIDE 4 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.
SLIDE 5
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
SLIDE 6
Survey methods – Western Port
Hansen et al. 2011
SLIDE 7
Survey methods – West Corner Inlet
SLIDE 8 Fish-eating birds
Surface seizers Australian Pelican Underwater pursuit Great Cormorant Pied Cormorant Little Pied Cormorant Little Black Cormorant 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
- 14 species (13 spp. ate >40% fish in their diets)
- 9 species breed in Western Port, other 5 species
recorded breeding in Victoria
- Fall into 5 feeding guilds
SLIDE 9 Fish-eating birds (14 species)
R² = 0.2617 200 400 600 800 1000 1200 1985 1990 1995 2000 2005 2010 2015 NUMBER OF FISH-EATING BIRDS
Total fish-eating birds in summer (Western Port)
TOTAL (Western Port)
SLIDE 10 Fish-eating birds (14 species)
R² = 0.62 200 400 600 800 1000 1200 1400 1600 1800 2000 1985 1995 2005 2015 NUMBER OF FISH-EATING BIRDS
Total fish-eating birds in summer (Corner Inlet)
Total (Corner Inlet) Linear (Total (Corner Inlet) )
SLIDE 11 Fish-eating birds in summer (Western Port & Corner Inlet)
.
R² = 0.2617 R² = 0.62 200 400 600 800 1000 1200 1400 1600 1800 2000 1985 1995 2005 2015 NUMBER OF FISH-EATING BIRDS TOTAL (Western Port) Total (Corner Inlet)
SLIDE 12 Fish-eating birds in winter (Western Port & Corner Inlet)
R² = 0.305 500 1000 1500 2000 2500 1985 1995 2005 2015 NUMBER OF FISH-EATING BIRDS Total (Corner Inlet) Winter Total (Western Port) Winter Linear (Total (Western Port) Winter)
SLIDE 13
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
SLIDE 14 Trends in tern numbers in Western Port (summer)
FAIRY/LITTLE TERN TRENDLINE R² = 0.18 CRESTED TERN TRENDLINE R² = 0.29 50 100 150 200 250 300 1985 1990 1995 2000 2005 2010 2015 NUMBER OF TERNS CASPIAN TERN FAIRY/LITTLE TERN CRESTED TERN Linear (FAIRY/LITTLE TERN) Linear (CRESTED TERN)
SLIDE 15
Crested Terns in summer and annual commercial catch
SLIDE 16 Numbers of breeding Royal Spoonbills in Western Port & Corner Inlet
R² = 0.24 R² = 0.36 50 100 150 200 250 1985 1990 1995 2000 2005 2010 2015 WESTERN PORT CORNER INLET Linear (WESTERN PORT) Linear (CORNER INLET)
SLIDE 17 What do Crested & Fairy/Little Terns eat?
Crested Tern Anchovy Engraulis australis Jack Mackerel Trachurus declivis Barracouta Thyrsites atun 93% frequency of
chicks at Nobbies, Phillip Island Chiaradia et al. (2002) Fairy/Little Tern Pilchard Sardinops sagax Anchovy Blue sprat Spratelloides robustus Mostly fish Taylor & Roe (2004)
Main fish in diet % fish in diet
Royal Spoonbill Bridled Goby Arenigobius bifrenatus 23% wet weight of prey in Western Port Lowe (1982)
SLIDE 18 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
SLIDE 19 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
SLIDE 20 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
SLIDE 21
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 volunteers 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.
