Annual Report: Breeding Activity

It can be argued that recording breeding events is the most important aspect of bird study since if the birds do not breed they will soon be extinct!  It is however a more difficult task than simple observation as:

• many birds go to some lengths to conceal their nests; and
• it is necessary to be very cautious with most species to avoid frightening the birds away from the nest.

To ameliorate these problems a wide definition of breeding is employed with the core events of "nest with eggs" and "nest with young" supported by a range of other, indirect, measures of breeding activity ranging from breeding display to dependent young.  To be rated as dependent young the fledglings must be out of the nest and generally be seen being fed by the parents or, in the case of waterbirds, be incapable of flight.  An exception is made for the Tawny Frogmouths where the fledglings are fed at night and it isn't possible to determine how this is achieved.  In that case the young are considered dependent until they move away from the parents some 10 weeks or so after leaving the nest.

(In other countries such as Canada studies are undertaken which assume all birds seen or heard  during the breeding season are in fact breeding.)

The number of records of each type over the 5 years of the project is in the table below.

Type of breeding activity	Number of  records
not coded	108
carry food	5
copulate	3
display	12
dependent young	90
Inspect hollow	1
nest building	16
nest with eggs	5
nest with young	33
bird on nest	28

Since this project commenced 303 breeding records have been noted. The decision to use the COG Breeding codes was made in late 2009 and thus approximately 1/3rd of the records are not coded to type of activity.  Such is life!  With respect to the analysis of the months where codes are available, the high proportion of records of dependent young is typical: note that this may not mean that the nest site was in the area.

7 species have been recorded breeding in 10 or more periods (year/month combination) accounting for 95 records (31.3% of all records) in total.  At the other extreme 23 species have a single breeding record and 12 species have been recorded twice as showing breeding activity.

A difficulty with analysis of breeding records is that the peak breeding period in the Southern Hemisphere is split by the change of year.  This is illustrated in the following chart.

 To overcome this I commenced, in mid 2009, recording the month in which observations were made and it is possible from that point on to re-categorise observations to a "breeding year" (running from July to June).  It might be noted that 78% of the records after December are coded as dependent young.

Following from this, the next section mostly covers 2 breeding seasons ending on 30 June 2011: the 2011-12 season will, inshallah, be reported on next year.

The records for 2009-10 show 58 breeding records whilst in 2010 -11 123 breeding events have been recorded.  In view of the number of events recorded in the first half of 2011-12  I believe this reflects extra effort by myself in recording information from 2010 onwards rather than an increase in amorousness of the
birds.  I shall endeavour to keep up the work moving forward but in view of the better effort in 2010-11 will restrict what follows to that breeding season.

In 2010-11 50 species were recorded as breeding and have been indicated as such in the monthly reports.  The number of months in which breeding was recorded, by the number of species performing this way, is shown in the following table.

# months breeding	# species
1	22
2	14
3	5
4	5
5	3
7	1

Australian Magpie was recorded as breeding in 7 months: 'on nest' in August and September 2010 and then dependent young until February 2011.  (I sometime times feel that a new code is needed for "indolent young" when the Magpie chicks are clearly able to fend for themselves but would rather bludge off their parents.)

The three species with breeding behaviour recorded in 5 months are Yellow-rumped Thornbill, Red Wattlebird and Willie Wagtail.  Again the dependent young category extends the breeding season for each species although one Willie Wagtail family appears to have attempted a second brood in February.

Links to Other sections of this report.
Overview; 2011 cf other 4 years; 2011 cf 2010