Birds of the Coastal Forest of Mambo Wetlands Reserve

Birds of the Coastal Forest of Mambo Wetlands Reserve

By Neil Fraser
Hunter Bird Observers Club

A quick overview of what we’ll look at in this article.

• Mambo’s Coastal Forest, its habitats and its most common bird species
  • Mambo’s coastal forest
  • Birds of the tree canopy
  • Birds of the mid-stratum
  • Birds of the lower shrub & ground layer
• How healthy are Mambo’s forests?
  • Main threats to the forest
  • Measuring health of an ecosystem is complex
  • Key species keeping the forest healthy
• Long term declining population trends for some species
  • Populations of key species are in decline, with none seen in recent years
  • Population decline in other species
• Factors driving change
  • Common insects in coastal forests and their roles
  • What is driving insect decline?
• Is Mambo at risk?
• Why are Mambo’s coastal forests important?

Mambo Wetlands Reserve is located in Port Stephens on Salamander Bay, extending north of Salamander Way to the coastal fringe of the bay (beyond Foreshore Drive).

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Mambo’s coastal forest

The coastal forest is mainly on the western edge of the reserve.

Two types of coastal forests are present in this area of Mambo (as described in Trees Near Me):

• Coastal Sands Apple-Blackbutt Forest
• Coastal Sands Swamp Mahogany Rush Forest

The distribution and type of birds within the forest is governed by the complexity of its structure, its vertical stratification, and resource availability

The main species or floral components of the Mambo coastal forests include:   

• Tree canopy: Smooth-barked Apple, Blackbutt, Red Bloodwood, Swamp Mahogany
• Mid-stratum: Old Man Banksia, Wallum Banksia, Coastal Banksia, Tree-broom Heath, Lemon-scented Tea Tree, Prickly Tea Tree
• Lower shrub layer: Bracken Fern, Spiny Mat Rush, Tassel Rush, Swamp Water Fern
• Ground layer: mosses, fungi, lichen

Birds of the tree canopy

The tree canopy birds are a mixture of large, mobile birds that move around following the availability of food resource. Mambo’s coastal forest with its mix of forest species provides blossom at multiple periods annually.

Although most birds have a dominant food type, they also consume small amounts of other foods to obtain a balanced diet.

Rainbow Lorikeet, Scaly-breasted Lorikeet, Red Wattlebird and Scarlet Honeyeater mainly feed on nectar

Eastern Rosella, Noisy Friarbird and Yellow-faced Honeyeater have a mixed diet of nectar, fruit and seeds

The mixture of tall trees species, 10-20m, form a canopy that provides food, nest sites, and observation perches. The canopy facilitates migratory movement for some smaller species.

Food

• Blossoms – parrots, honeyeaters, friar birds, wattlebirds 
• Insects – lerps, aphids, larvae, caterpillars, flies, crickets – and spiders
• Perches for insect hawking – cuckoo-shrikes, wattlebirds, grey fantails.

Nesting sites

• Hollows – cockatoos, most parrots, kookaburras, wood ducks, owls, pardalotes, dollarbirds, treecreepers
• Safe nest building sites – raptors, corvids, currawongs and larger birds.

The canopy reduces light reaching lower layers allowing less hardy shrubs to flourish.

Birds of the mid-stratum

Medium size honeyeaters and insectivorous species dominate the mid-stratum.

The White-cheeked Honeyeater, Little Wattlebird, Brown Honeyeater, Eastern Spinebill and Lewin’s Honeyeater feed on nectar – note their long, curved bill

A healthy mid-stratum is diverse, with immature canopy trees and medium-sized shrubs 1-5m, including Banksia, Wattle, Melaleuca, Monotoca and Leptospermum.

The mid-stratum

• receives less light and is more protected from winds, protecting the underlying shrub layer
• provides habitat for small to medium birds, including food sources such as blossom, insects and fruit, while protecting them from avian predators.

Birds of the lower shrub & ground layer

Plants in the lower shrub layer are typically smaller than 1m, and include ferns, rushes, herbs, grasses and wildflowers.

The shrub layer provides dense shelter, abundant food resources, and a stable microclimate. The dense foliage also protects small birds from predators.

Most shrub layer plants have a short life span. The shrub litter decomposes rapidly, supporting efficient nutrient recycling, with plants having high concentrations of nitrogen, phosphorus, potassium and magnesium. The shrub layer provides an important food source of insects, arthropods and seeds.

Small, resident insectivorous birds dominate the birds of the lower shrub layer. Typically these birds have short, narrow bills.

The ground layer

The ground layer Is the engine of the entire forest ecosystem – it drives healthy growth. There are no true ground dwelling birds in the Mambo coastal forests.

• Flora on the ground layer includes mosses, fungi and lichen
• Decomposing leaf litter, bark, branches, trunks and stumps provides the nutrients for the entire forest ecosystem and is a rich medium for new plants to germinate. Retention of a rich and thick ground layer
  • prevents weed growth
  • conserves moisture
  • prevents erosion
  • enriches soil and fixes carbon
  • cultivates soil bacteria
  • provides habitat for insects, small reptiles, small mammals and some birds
  • rich source of insects and seeds for birds.

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How healthy are Mambo’s forests?

Mambo’s coastal forests appear healthy to the casual observer.

Main threats to the forest include ….

1. Habitat integrity, coastal development and urban pollution.

• Within the Mambo Wetlands Reserve, the coastal forest patch shown on the map has no habitat loss or fragmentation. However the Reserve is only a portion of a once much larger connected wetlands ecosystem, including the wetlands south of Salamander Way, west to Tilligery Nature Reserve in Taylors Beach, and east to include some of the current Salamander Central shopping centre. Roads and infill have disconnected the Reserve from its broader ecosystem.
• The proposed Salamander Bay Town Centre Place Plan earmarks the recovering coastal forests on its south-eastern extremity, directly west of the Tomaree Library, for multi-story development. This area was sand mined some 50 years ago and the spoils used for infill at the adjacent Woolworths site. This 50 year old regrowing endangered Swamp Forest is is an important buffer zone helping protect the Reserve from urban impact. Read more here.
• Pollution and urban runoff into the wetlands is unmonitored. 

2. Climate change and fire regimes

• No damage is evident to date from climate change or extreme weather.
• Fire regimes have had varied impact. The Coastal Forest last burnt in 2003. However, the freshwater wetlands and their surrounding swamp forests have had several fires in recent times. 

3. Invasive species and disease

• Some lantana and introduced grasses
• No evidence of die back from pathogens and disease

Measuring health of an ecosystem is complex

Birds are excellent indicators of forest health and ecosystem integrity

• Sensitive to environmental changes
• Relatively easy to observe
• Presence, diversity, and population trends provide information about the health of forest ecosystems

Chart shows the decline in the annual observed bird species over 10 years.

Shows total number of species recorded annually over 10 year. Data was collected from monthly early morning surveys with records for both visual observations and identified calls. Birds of the night, such as Tawny Frogmouths and Southern Boobooks are present but not recorded due to the timing of surveys.

Key species keeping the forest healthy

Treecreepers walk up trees with a circular pattern as they search for insects, prising off bark to locate the insects below.

Sittellas have short, sharp pointed bill for catching insects on the surface of tree trunks. They forage down the trunks and branches. 

Varied Sittella listed as Vulnerable NSW Biodiversity Conservation Act 2016

Populations of key species are in decline, with none seen in recent years

None of the four key forest health-keeper bird species critical to keeping forests healthy have been seen in the last three years.

In the charts below, analysis of the annual reporting rate (RR%) provides a measure of population change.

Only two records of White-throated Treecreeper occurred in Mambo in the last 10 years.

No records of Striated Pardalote in the last 10 years.

No key species were recorded in recent years.

Population decline in other species

The common factor in all these declining bird populations is that they are all insectivorous species.

White-throated Gerygone population decllne is statistically significant (P <0.05) 95% confidence level. The other species show a declining trend but the rate is not yet significant.

Some insectivorous birds in Mambo seem not to be declining

Not all insectivorous birds have declining populations. The Brown Thornbill, Grey Fantail populations appear stable, while the Variegated Fairy-wren population appears to be increasing.

Examples of different insectivorous groups:

• Small birds: thornbills, pardalotes, fairy-wrens, White-browed Scrubwren
• Medium size: Grey Fantail, Eastern Yellow Robin, Golden Whistler, Lewin’s Honeyeater
• Large birds: Australian Magpie, Laughing Kookaburra, Grey Butcherbird, Black-faced Cuckoo-shrike

Insectivorous birds eat 60% of all insects found in coastal forests and woodlands so have an important role in maintaining health of forests.

Common insects in coastal forests and their roles

Most insects live high in the canopy, and include sap suckers and pollinators.

• In the canopy they are closer to sun’s energy and being ectothermic (‘cold-blooded’) they regulate their body temperature and drive essential metabolic processes using heat from the sun.
• As adults in flight, they forage, evade predators, find mates, disperse, migrate, and can become food for birds, reptiles and small mammals.

In the ground layer other insects are the decomposers – turn plant litter into compost and recycle nutrients.

Spiders are a critically important food for many insectivorous birds. Spiders (though not insects they are in the same broader group of Arthropods), are very high quality food and one of the few sources of amino acids needed by birds when breeding.

What is driving insect decline?

Decline in woodland birds in temperate south-eastern Australia is well known – and they are mostly small to medium size insectivores and nectarivores.

Magnitude, rate and geographical extent of insect declines in Australia and their causative role in bird declines are not well understood

Drivers of insect decline as applied to Mambo Wetlands Reserve:

• Loss and fragmentation of habitat- Mambo is part of a highly fragmented urban landscape
• Urbanisation – noise, pets, disturbance, pollution
• Invasive species – plants and animals – feral dogs and cats, foxes, lantana, dumping of garden waste
• Ecosystem dysfunction – unknown
• Firewood removal – unknown
• Pesticides and fertilizers – use around homes creates lethal barriers to insect dispersal and migration
• Climate change – floods, higher tides, storms, higher temperatures
• Synergistic interaction of the above factors.

Is Mambo at risk?

The risk to Mambo is not possible to determine definitively with current knowledge, though we should always exercise the precautionary principle.¹

• Decline of woodland/forest birds is well studied and quantified, though the decline of insect species is yet to be researched.
• Population of some avian species in Mambo is declining – however is this a local trend or regional/national trend?
• Absence of species key to forest health is of concern.
• Impact of pesticides?
  • Pest control practices of surrounding properties can form an invisible lethal barrier for dispersing and migrating insects.

We cannot take the status of the Mambo Wetlands Reserve for granted – we need to remain vigilant and take precautionary actions.

Why are Mambo’s coastal forests important?

• Form an important part of the network of National Parks and Nature Reserves that surround Port Stephens
• Provide protected habitat for many forest species and protected shorelines and waterways for waterbirds and shorebirds
• Contain high levels of floristic diversity
• Crucial carbon sink
• Critical habitat for avian foraging, establishing territories and breeding
  • Eucalypts provide mass flowering for mobile honeyeaters, lorikeets
  • Mature tree provide nesting hollows
• Habitat for Koalas (Endangered species – NSW BC Act 2016)
• Improve air quality, prevent nutrient loss and soil erosion, improve water quality and reduce risk of flooding
• Green urban areas promote human health and well being.

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1. Precautionary principle ~ requires proactive measures are undertaken to prevent or minimise damage before it occurs, even without full scientific certainty, and the burden of proof is with the proponent of an activity to show it is safe, rather than the public to provide it is unsafe. ↩︎