Wednesday, 12 June 2013

Mistletoe and birds

This follows on from two previous posts on Mistletoes (here and there).  My principal reason for following up was receiving some comments suggesting that mistletoes were absent from the higher country because Mistletoebirds (Dicaem hirundinaceum) do not occur in the higher wet forests. (Steve Wilson's definitive book "Birds of the ACT: Two Centuries of Change" notes that a few Mistletoebirds were banded in the mountains but ".. it is rare in the ranges.".)

It seemed strange that Watson and Herring show mistletoes to be a keystone resource if the plants are so dependent on a single species of bird.  

According to them - both from their bibliography and the references in the text -the key resource on mistletoe- bird interaction is still "Reid N  "Pollination and seed dispersal of mistletoes (Loranthaceae) by birds in southern Australia." published in  "The Dynamic Partnership: Birds and Plants in Australia" Ford and Paton (eds) 1986.  It seemed like an interesting volume, despite its vintage, so a copy was acquired (thank you Lost and Found Books).  As well as the article by Reid, "Forde N "Relationships between Birds and Fruits in temperate Australia." " was relevant to my enquiries.

The following table contains all species identified by Reid as feeding on nectar or seeds from Mistletoe species.  In addition the species shown in green were reported by Forde, but not by Reid.  The species marked in red are those which are considered by Reid (in another paper) to be the only species "undeniably involved in mistletoe dispersal".

ACT status
nectar feeders
seed feeders
COMMON Striated Thornbill Gang-gang Cockatoo
Brown Thornbill Galah 
Eastern Spinebill Crimson Rosella
Yellow-faced Honeyeater Eastern Rosella
White-eared Honeyeater Fuscous Honeyeater 
Noisy Miner White-plumed Honeyeater
Brown-headed Honeyeater Red Wattlebird
Noisy Friarbird White-naped Honeyeater
Black-faced Cuckoo-shrike
Olive-backed Oriole
Pied Currawong
Grey Currawong
Australian Raven
Little Raven
Silvereye
Common Starling
Common Blackbird
Mistletoebird 
LESS COMMON Yellow-tufted Honeyeater Emu
Scarlet Honeyeater Cockatiel
Crescent Honeyeater Little Lorikeet
New Holland Honeyeater
Masked Woodswallow
White-browed Woodswallow
RARE Chestnut-rumped Thornbill White-fronted Honeyeater
Lewin's Honeyeater Spiny-cheeked Honeyeater
Tawny-crowned Honeyeater Little Wattlebird
Regent Honeyeater
Painted Honeyeater
NOT RECORDED IN ACT Purple-crowned Lorikeet Brown Cuckoo-Dove
Inland Thornbill Rose-crowned Fruit-Dove
Purple-gaped Honeyeater Red-winged Parrot
Yellow-plumed Honeyeater Blue Bonnet
Grey-fronted Honeyeater Mulga Parrot 
Brown Honeyeater  Australian (Mallee) Ringneck  
White-cheeked Honeyeater Pied Honeyeater
White-throated Honeyeater Singing Honeyeater
Yellow-bellied Sunbird  Yellow-throated Miner
Grey Honeyeater
Striped Honeyeater
Little Crow
Torresian Crow
Metallic Starling
The two columns show that some species are known to take nectar from the flowers (playing an important role in fertilisation of the species) while others are known to be frugivorous.  Several authors note that some of the seed eaters - especially the parrots and their close relatives - are seed predators in that they damage the seeds beyond the ability to germinate.

I have also categorised (heuristically I am afraid) the bird species according to their occurrence around Canberra.  Of the birds common around Canberra, the Mistletoebird is the only 'proven disperser' of mistletoes but there are a good number of non-predator seed feeders in the area.  Many of these, including Red Wattlebird. White-naped Honeyeater, and Pied Currawong are common in the Ranges and could be expected over a number of years to have introduced mistletoe seeds to the area.

That we have not recorded Amyema sp. in the Ranges cannot be due solely to the absence of Mistletoebirds.  I suggest next time a WW goes into the Brindabella Ranges keeping an eye upwards would be a good idea !

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