Companies are looking for iPhone and Android software engineers and discovering that there are just not enough mobile developers out there.

In the last year, the number of online job listings with the keyword "iPhone" in the text has nearly tripled, while the number with "Android" has more than quadrupled, according to listings search engine Indeed.com.

To fill the gap many companies are retraining their software engineers to undertake mobile development and the other effect of the shortage is an upward pressure on wages. In an October 2010 survey by Dice.com about 31% of companies reported that average pay among mobile software designers and engineers increased at a higher rate than normal, mostly because of heightening competition for talent.

The Dice survey reported the average mobile salary last fall as about $76,000, but several companies claimed to pay experienced mobile developers anywhere from $90,000 to $150,000 a year.

The situation in the UK is very similar. Vacancies for developers with Android skills have rocketed by 424% in the space of a year, according to specialist IT recruitment consultancy IntaPeople which commented:

Such rapid growth shows that it makes commercial sense for IT professionals to sharpen their development abilities on both the Android and iPhone platforms.

Demand for developers with Android experience grew at a much faster rate than for those with iPhone expertise, which rose by a more moderate 263%. However, the overall number of iPhone-related positions remained higher, with 1,239 jobs advertised between November 2010 and January 2011, compared to 1,047 for Android.

The average salary for a developer with Android experience was found to be £45,000, while those with iPhone skills can expect to receive £42,500.