(1) Garden Count.

This is by far the simplest level of count and doesn’t require you to leave home to do it.  It has been used by Canberra Ornithologists Group over many years in their Garden Bird Survey.  The method is based on counting the maximum number of birds seen within a 100 metre radius of your house (an area of around 3 hectares) at any one time during a week. The first three hours of daylight are usually when you see most birds, but if you see a big flock in your garden at some other time of day – record it as your maximum for the week.

You can, of course, use this method at home or anywhere else that you spend a significant amount of time, eg at work.  Geocode your study site with a Geographic Positioning System.  Record the counts into a tally book, or better still into a spreadsheet such as Microsoft Excel.  One garden on its own is unlikely to be representative of say a whole suburb.  Try to encourage colleagues to do similar counts nearby so you can average counts across a suburb or other designated area. Note that the Sydney-based Birds in Backyards project also uses a Garden Bird Count, but the method is a little more complex and time restricted than the Canberra scheme – see website below.

(2) Transect Counts

In areas with high myna densities belt (or strip as they are sometimes known) transect counts are a simple, repeatable way of assessing myna density.  Because transects cover a much larger area than a garden count, they are likely to give more representative information about myna numbers.  Transects should be around 2000 m long and around 100 m in width in open areas – narrower if visibility is low.  You need to estimate length and width reasonably accurately from a map so that you can estimate the area searched, because once you’ve counted all the mynas in that area you can extrapolate to the number of mynas per km². Geocode the start and finish of your transect with a Geographic Positioning System.  Transects need to be representative of the study area, but also convenient for you to traverse; circular routes are good so that you can leave your house or park a car and return to it at the end of the transect.  Walking or slow cycling are good ways to count mynas on transects.  Hand-held tally counters are useful
(eg, http://www.prospectors.com.au/p-3551-hand-tally-counter.aspx).  Record the counts into a tally book, or better still into a spreadsheet such as Microsoft Excel, which greatly facilitates calculating averages.

(3) Communal Roost Search

Locating myna roosts is best done in the 20 minutes or so either side of sunset, when mynas from surrounding areas progressively congregate near their communal roosts and eventually fly into a particular tree, or trees, where they settle for the night.  Which tree is used may vary over seasons, but, if undisturbed, birds may return repeatedly to particular sites, sometimes over many years. Mynas also chorus, but more briefly, before they leave the roost in the morning.

The most effective method of locating roosts in new areas is by listening for roosting choruses while driving slowly in a quiet vehicle with the windows rolled down, or by bicycling; walking is too slow to be very useful, unless the general location of a roost is known beforehand. If a vantage point enables an overview, it can be useful to watch for mynas flying toward a central area and then use car or bike to search it.  Several search sessions, perhaps once a month, or season, are usually required to ensure that all roosts in the search area are located. Geocode the sites with a Geographic Positioning System.  If all the roosts in a particular area can be located and the occupants counted it is possible to come up with an estimate of the total myna population in that area.  Except during the breeding season, all the mynas in that area will roost in one or other of the communal roosts.

Once a “quorum” of birds has gathered in the roost tree(s) they begin their communal roost chorus, which, with a roost of >100 birds, can be very loud (>120 dB @ source) and heard >500 m away.  Smaller aggregations make less noise, and tend to call intermittently, so are not as easy to detect as larger groups.  Very small groups, <20 or so, may hardly chorus at all. Mynas may roost alone or with other species, such as European Starlings, Metallic Starlings and various species of Lorikeet.

The time available each day for searching by listening for roosting choruses is quite limited (as little as 20 min. in tropical areas, depending on the weather, time of year and the number of birds in the roost).  The ability of observer(s) to hear the roosting chorus is compromised by excessive engine noise, wind noise created by the vehicle moving rapidly, as well as noise from eg. traffic and children playing and the prevailing weather conditions, eg rain on the roof of the vehicle.  Chorusing time may be extended if the roosts are near high levels of ambient lighting, eg street lights.

The roosting chorus, ie the detection period, can be extended by 30 min or so after the usual “shut-down” time by call playback of a chorus recording, from eg a CD; this causes nearby roosting birds to respond. This is mainly useful for checking the presence/absence of mynas at pre-known sites.

Estimating numbers of occupants of communal roosts

With roosts of less than say 200 it is possible to get a good estimate of the number of occupants by direct counting, although this is complicated because birds may rapidly fly in and out of the roost repeatedly before settling down for the night.  At least two tally counters (more with >1 species) are required to keep track of how many birds enter the roost and how many leave; the number of occupants is the difference between the two.