Annual Report 2012: Breeding Activity

It can be argued that recording breeding events is the most important aspect of bird observation 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. (I sometimes 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.) 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.  

I have made an exception 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 6 years of the project is in the table below.

Type of breeding activity	Number of Records
not coded	110
carry food	6
copulate	3
display	19
dependent young	159
Inspect hollow	2
nest building	29
nest with eggs	5
nest with young	55
bird on nest	47

Since this project commenced 439 breeding records have been noted. The decision to use the COG Breeding codes was made in late 2009 and thus approximately 1/4th 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 'financial year" 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.  The incidence of type of event x month is illustrated by this chart.

Following from this, the next section mostly covers 3 breeding seasons ending on 30 June 2012 the 2012-13 season will, inshallah, be reported on next year, but at this stage appears similar to history.

The records for 2009-10 show 58 breeding records, 2010 -11 123 breeding events and for 2011-12 137 breeding events have been recorded.  The increase in the number of events recorded since 2009-10 reflects extra effort by myself in recording information from 2010 onwards rather than an increase in amorousness of the birds. I shall not consider the 2009-10 season further in this analysis.  

In terms of number of events, I don't consider the increase between the last two years significant.

In 2010-11 51 species were recorded as breeding while an almost identical 52 species were recorded in 2011-12.  These have been indicated as such in the monthly reports.  

The number of reports received by species is summarised in the following table.

# reports	# species
1	17
2	13
3-5	17
6-9	11
10+	4

As expected most species have only been reported undertaking breeding activity once or twice.  The four species with 10 or more breeding records are:

• Striated Pardalote (10 reports): a common species which often nests in hollows around buildings and frequently calls when in the nest. 
• Australasian Grebe (11 reports): commonly seen on farm dams with nests in the open.  The young birds are both noisy and distinctive,  
• Willie Wagtail (13 reports): The records for this species cover a wide range of types of "nest-centred" events, possibly reflecting the energetic distraction displays, having the unintended outcome of lading keen observers to the nest (rather than away from it).
• Australian Magpie (19 reports): the swooping of defending adults and the whingeing of the dependent young are hard to ignore, however much one tries.

I would note that the Tawny Frogmouths just fail to make the 10 record category since one nest site has been recorded as active for 4 and 5 months respectively over the 2 seasons covered.  A second site has been reported for the 2012-13 season so these excellent birds should crack the big league next year!

Links to Other sections of this report.

Overview; 2011 cf other 5 years; 2012 cf 2011