Annual Report 2014 Breeding

Breeding birds

The preamble to this post is copied from last year.  That makes this report more self-contained, which I see as a Good Thing.  

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 International eBird project, run out of the prestigious Ornithology Programme at Cornell U in New York takes a very broad view with codes such as “Singing male” (Possible breeding) and “Agitated Behaviour” (Probable breeding).  Of course, with this wide set it is possible to choose I shall stick with the set of codes used by COG.

The percentage of records of each type over the 8 years of the project (separately shown for the last complete 'season (2013-14) and the rest of the records is in the chart below.

There does not look to be any significant difference with "dependent young" dominating in both categories.  Note that some of the codes (eg DY) may not mean that the nest site was in the area.

Since this project commenced 654 breeding records have been noted. The decision to use the COG Breeding codes was made in late 2009 and thus approximately 1/5th of the records are not coded to type of activity.  Such is life, and the uncoded records are excluded from the above!  

A difficulty with analysis of breeding records is that the peak breeding period in the Southern Hemisphere is split by the change of calendar 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 81% of the records after December are coded as dependent young (the percentage didn't change after adding another year of records).  The incidence of type of event x month is illustrated by this chart in which the redder fill indicates a greater number of records) .

Following from this, the next section mostly covers 4 breeding seasons ending on 30 June 2014. The 2014-15 season will, inshallah, be reported on next year, but at this stage appears similar to history.

Season	# records
2010-11	124
2011-12	137
2012-13	105
2013-14	118

It is difficult to assign reasons for the differences shown in this table - I might try to do a separate post on this later, when feeling particularly masochistic.

Taking the number of species seen in each season the following result is obtained.  My impression is that the number of breeding species is a little more stable that the number of breeding records.  

Season	# species
2010-11	51
2011-12	54
2012-13	49
2013-14	47

In summary the following is found:

Bred in both seasons:    27 species
Bred in 2012-13 only    22 species 
Bred in 2013-14 only    20 species     

I have attempted to identify any factors common (looking at things like broad groups of birds; rarity, migrant status) between the birds in the three groups and failed to do so.  I think this resolves to an observation that breeding records are damn difficult to get.  

The number of reports received over the 8 calendar years by species is summarised in the following table.

# reports	# species
1	35
2-4	33
5-10	20
11-19	13
20+	7

As expected a large proportion of species have only been reported undertaking breeding activity a few times.  The seven species with 20 or more breeding records are:

• Australian Magpie (50 reports): the swooping of defending adults and the whingeing of the dependent young are hard to ignore, however much one tries.  That being said no-one reported breeding behaviour by  Magpie in 2013-14 - I didn't even ge swooped riding my bike!  The situation has returned to normal for 2014-15!
• Tawny Frogmouth (28 reports): Once noticed the nest and parents with dependent young are easy to relocate.  Also the breeding season is 5 months long from the start of nesting to kicking the young out.
• Pied Currawong (28 reports): see Australian Magpie.  There is no way I can miss the <expletives deleted, with regret> pair that nest above our lawn and swoop me every time I walk across it!
•  Willie Wagtail (26 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 leading keen observers to the nest (rather than away from it).
• Striated Pardalote (24 reports): a serial offender at building a nest in any apparent hole in a building or tree.  Also very vocal when doing so!  This species re-entered the top list after dropping out in 2012-13
• Welcome Swallow (22 reports):  Similar to the previous species but prefers a more open site such as in the rafters of a shed.  
• Yellow-rumped Thornbill (20 reports): Very common species and feeding young often happens out in the open.

The score for Australasian Grebe continues to be affected by our top dam being deserted this year, but again the nests were far less obvious around the district.  Is this an impact of the dry period after last Summer?

Links to other sections of this report

Overall picture
Comparison with 2013
Comaprison with earlier years