The most striking result this year was a large decline in the number of silvereye counted (average about two thirds the number counted last year).Survey participants made comments such as, “Where are all the silvereyes?” and “This is the lowest number of silvereyes we’ve had in years”.
House sparrow was by far the most numerous species this year (second last year), with 39,001 counted in 3089 gardens (average 12.6 per garden). Silvereye was second (top last year) with 18,641 counted (average 6.0 per garden). As in previous years, counts varied between regions. When the average counts for each region were weighted by the proportion of households in each region, the national average count for house sparrow was 13.0 and silvereye 5.5 (Table 1).
Starling and blackbird again had the third and fourth highest counts nationally. Myna had the 5th highest count nationally but the 3rd highest in Auckland, behind house sparrow and silvereye (Table 1). Tui had the 6th highest count nationally but only the 28th highest in Canterbury. Silvereye, tui, and fantail (7th highest count nationally) were the only native species in the top 10.
Table 1 Top 10 birds in 2011 (average number per garden).
The national average was calculated from regional averages weighted by regional proportions of households.
Trends over the first 5 years
The long-term aim of the survey is to determine trends in bird numbers over time. In particular, we want to know if the numbers of native birds such as tui, bellbird, kereru, fantail, and grey warbler are increasing or decreasing in our gardens.
The survey has been running for 5 years now, but it is still too soon to determine whether changes in the numbers of birds counted are just part of normal fluctuations over time or part of a long-term trend. Counts of house sparrow increased over the first 4 years (2007 to 2010) then declined slightly this year (Figure 1). The increase from 2007 to 2010 may have been in response to an outbreak of salmonellosis in 2000, which caused major mortality in house sparrow populations in many parts of the country (i.e. the species may have been still recovering from the disease outbreak), or it may have been in response to some other factor (e.g. favourable environmental conditions).
Silvereye counts declined from 2007 to 2009 (the first 3 years of the survey), increased markedly in 2010, and then declined markedly in 2011 (Figure 1). The decline from 2007 to 2009 occurred mainly in Otago and Southland, and mainly in gardens with sugar-water feeders. It may have been caused (or partly caused) by a disease called avian pox. The decline in 2011 may have been a consequence of the mild winter. The lack of snow and frosts may have meant there was still plenty of natural food around in forested areas, so birds were not forced into gardens in search of food.
The counts of other species did not change as much as the counts of house sparrow and silvereye (Figure 1).
|Figure 1 Average counts of the 12 species that have occurred in the top 10 in one or more years, 2007–2011
(calculated from regional average counts weighted by regional proportions of households).
Dunnock is sometimes confused with female house sparrow. Major differences are the dunnock has a fine pointed bill (for eating insects) and is generally solitary, not far from cover, whereas the house sparrow has a much thicker bill (for eating seeds) and occurs in flocks out in the open.
A total of 85 species of birds were detected in (or from) gardens in 2011. However, 11 of these species were detected in (or from) just one garden. These included Australasian crested grebe (from a rural garden near Lake Hawea, Otago), brown teal (from a rural garden near Matapouri, Northland), little blue penguin (under floor of house in an urban garden, Paekakariki, Wellington), little black shag (from an urban garden on the shore of Lake Pupuke, Auckland), spotted shag (from a coastal rural garden near Dunedin, Otago), long-tailed cuckoo (heard and seen from a rural garden near Egmont Village, Taranaki), shining cuckoo (from a rural garden near Oropi, Bay of Plenty), royal spoonbill (from a rural garden, Opaki, Wellington), takahe (from a rural garden near the predator-free Maungatautari Ecological Reserve, Waikato), tufted guineafowl (domesticated in a rural garden in Waihopai Valley, Marlborough), and fernbird (in a rural garden near Okiato, Northland).
Another 23 species were detected in (or from) fewer than 10 gardens, including Australian coot, New Zealand shoveler, New Zealand dabchick, Caspian tern, Pacific golden plover, banded rail, little owl, morepork, brown creeper, cirl bunting, pipit, red-crowned parakeet, rifleman, rook, stitchbird, and sulphur-crested cockatoo. The number of records of these species is too few for determining their population trends (unless they increase in abundance markedly in the future).
Several instances of unusual behaviour were reported. For example, house sparrows were reported drinking sugar-water from sugar-water feeders. Their normal food is seeds of cereals such as wheat and barley, grasses, and weeds such as fat hen. However, they have been reported robbing nectar from flowers, so it is perhaps not surprising that on occasions they also drink sugar-water.
Chaffinches were reported eating fat from hanging fat-balls by hovering beside the fat-balls. They normally eat seeds, invertebrates, and small berries from the ground, though they do hawk for flying insects. The hovering beside fat-balls is a bit like hawking. More often chaffinches are seen on the ground under fat-balls, eating fat spilled by other birds, such as silvereyes and starlings.
One survey participant reported a grey warbler eating apple-and-cinnamon cake put on an outdoor table for house sparrows. This is very unusual behaviour because grey warblers normally eat insects, though they do occasionally eat small berries. Also, cinnamon is normally repellent to birds, though the amount in the cake was presumably insufficient to induce avoidance. The grey warbler was also seen ‘warbling’ to its reflection in a bedroom window, and its pear-shaped nest was found nearby.
Comments from participants
Many participants made additional comments about the survey and the birds they saw. Below is a small selection of comments.
“I thoroughly enjoy doing the garden bird survey. It has taught me to slow down when outside and look and listen. The first survey showed me that we had a semi-resident kereru frequenting a weeping willow tree and our many kowhai trees. That was my first sighting of one here. Since then I frequently see them, because I look and listen! Nice one!!!”
“My young boys aged 7 and 4 were helping or should I say making more noise and chasing the birds! It was great fun though.”
“Loved doing the survey with 7 yr old granddaughter.”
“My 10 yr old has been bird watching and identifying birds since he was 2.”
“The survey was shortened by the karearea (New Zealand falcon) zooming through – everything disappeared for 20 minutes or so!”
“Note when magpies come other birds disappear for few minutes then come back after magpies have fed.”
“The magpie was getting water out of the leaf of a succulent in a pot on the deck. Never seen that before.”
“I open pine cones on top of the log fire and then place them on the terrace where we can observe easily. We have found greenfinches are the dominant ones chasing all away except magpies.”
“Since putting out Wild Bird Seed for finches early last year, we have had an influx of spotted doves (and house sparrows) who poop on our roof so we have stopped putting out seed!”
“Mum has a bird feeder which she puts seeds in. Mostly only sparrows come, however recently the yellowhammers have found their way to it.”
“We still have 40+ kereru most days but I didn't see all of them during the survey.”
“I have had up to nine kereru at one time feeding on young tree lucerne.”
“There have been two attacks I know of by domestic cats on kereru. Thankfully not successful. Can't we outlaw cats...It is against the law for me to kill native birds but I can own a cat (I don't) that will do it for me...urrr...what is that about?”
“Too many cats here and they devastate the bird life. I would love to feed the birds but in turn I would be feeding the cats!”
“In the area we live in we have seen a large increase in mynas this year, sometimes having as many as 30 in the garden at a time.”
“Silvereyes came after mynas had gone.”
“Silvereyes love banana in the early cold mornings. Their numbers always increase as word gets out!”
“There are a lot less silvereyes this year and they were very late arriving.”
“The milder winter appears to have made a vast difference to silvereye numbers (usually 200+ but only 25 this year).”
The total number of survey returns (3089) was slightly lower than last year (4193). Most survey returns came from Wellington (25%), followed by Canterbury (16%), Otago (15%), and Auckland (12%). The largest drop in number of survey returns was from Canterbury as a result of the earthquakes (16% this year compared with 30% last year, from 14% of the national households). The number of survey returns from Auckland continues to be low (12% this year compared with 11% last year, from 30% of the national households). Otago contributed the most survey returns on a per household basis (15% of returns from 5% of households). Other regions contributing ‘above their weight’ included Wellington (25% of returns from 12% of households) and Marlborough (2% of returns from 1% of households). The largest increase in the number of survey returns was from Hawke’s Bay (5.6% this year compared with 3.4% last year, from 3.8% of households).
Survey forms were published by the Dominion Post (Wellington), The Press (Christchurch), and Otago Daily Times (Dunedin), as well as by Forest & Bird magazine. Unfortunately, The Press did not include a return address on the survey form, so few returns were received from that source (see below). Of all returns, 37% were entered directly online by participants, and 67% by volunteer data-entry operators. Of the hard-copy returns entered by volunteers, 31% were from the form downloaded from the website, 21% from the Dominion Post, 19% from forms handed out to people, 12% from Forest & Bird magazine, 11% from the Otago Daily Times, 4% from The Press, and 2% from other sources (email, telephone, etc).
Table 2 Source of garden bird survey returns received in 2011.
|Source||Number received||% received||% hardcopy|
|Online data-entry by participants||1148||37.2||-|
|Paper form printed from Web||607||19.7||31.3|
|Newspaper form (Dominion Post)||411||13.3||21.2|
|Paper form handed out (9,400)||365||11.8||18.8|
|Forest & Bird magazine form (14,000)||237||7.7||12.2|
|Newspaper form (Otago Daily Times)||210||6.8||10.8|
|Newspaper form (The Press)||72||2.3||3.7|
|Other sources (e.g. letter)||39||1.2||2.0|
In addition to the above, there were about 120 returns from a variety of sources that were invalid (e.g. because only the presence of species not numbers of birds were recorded, the surveys lasted all day or all week not 1 hour, the surveys were repeat surveys at the same address, or the surveys were done before or after the official survey period). Also, there were 67 returns from parks, 38 from school grounds, and 27 from other locations.
This survey was possible only thanks to the large number of volunteer participants who counted birds in their gardens. Thanks also to Landcare Research for promoting the survey, funding the printing of the survey form, and providing programmer and webmaster support; Forest & Bird, Ornithological Society, newspaper, radio, and television companies for promoting the survey; T. Marshall for designing the survey form; and about 40 volunteers for helping enter the data into the computer.